Methods for determining transition metal compound concentrations in multicomponent liquid systems

ABSTRACT

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems.

REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/939,446, filed on Mar. 29, 2018, now U.S. Pat.No. 10,507,445, the disclosure of which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present disclosure concerns methods for determining theconcentrations of transition metal compounds in solutions containingmore than one transition metal compound, and more particularly relatesto the use of UV-Vis (ultraviolet-visible) spectroscopy forsimultaneously determining the respective concentrations of individualtransition metal compounds.

BACKGROUND OF THE INVENTION

Polyolefins such as high density polyethylene (HDPE) homopolymer andlinear low density polyethylene (LLDPE) copolymer can be produced usingvarious combinations of catalyst systems and polymerization processes.In many olefin polymerization processes, a catalyst system containingmore than one transition metal compound is utilized. Precisedetermination of the relative and absolute concentrations of eachtransition metal compound allows for better control of thepolymerization processes and the resulting polymer products. It would bebeneficial if real-time monitoring or measurement of the respectiveamount of each transition metal compound present in catalyst feedstreams, catalyst systems, and polymerization reactor systems could beperformed in order to improve the control of the polymerization process.Additionally, it would be beneficial to determine the respectiveconcentrations of a first transition metal compound and a secondtransition metal compound in solutions where the UV-Vis spectrums of thefirst transition metal compound and the second transition metal compoundoverlap, and/or where the second transition metal compound is in largeexcess relative to the first transition metal compound. Accordingly, itis to these ends that the present invention is generally directed.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify required oressential features of the claimed subject matter. Nor is this summaryintended to be used to limit the scope of the claimed subject matter.

Methods for determining a first concentration of a first transitionmetal compound and a second concentration of a second transition metalcompound in a solution containing the first transition metal compoundand the second transition metal compound are disclosed herein. Inaccordance with an aspect of the present invention, one such method cancomprise (i) providing a first reference absorbance profile (F₁) of thefirst transition metal compound in a first reference solution at a firstknown concentration, and a second reference absorbance profile (F₂) ofthe second transition metal compound in a second reference solution at asecond known concentration, (ii) submitting a sample of the solution toa sample chamber, (iii) irradiating the sample in the chamber with alight beam at a wavelength in the UV-visible spectrum, (iv) generating asample absorbance profile of the sample, and calculating a curve havingthe formula β₁F₁+β₂F₂ to fit the sample absorbance profile to aleast-squares regression fit value (R²) of at least 0.9, wherein β₁ is afirst weighting coefficient, F₁ is the first reference absorbanceprofile of the first transition metal compound in the first referencesolution at the first known concentration, β₂ is a second weightingcoefficient, and F₂ is the second reference absorbance profile of thesecond transition metal compound in the second reference solution at thesecond known concentration, and (v) multiplying the first knownconcentration with β₁ to determine the first concentration of the firsttransition metal compound in the solution, and multiplying the secondknown concentration with β₂ to determine the second concentration of thesecond transition metal compound in the solution.

In another aspect, a process for operating a polymerization reactorsystem is disclosed, and in this aspect, the process can comprise (I)contacting a catalyst system comprising a first transition metalcompound, a second transition metal compound, an activator, and anoptional co-catalyst, with an olefin monomer and an optional olefincomonomer in a reactor within the polymerization reactor system underpolymerization reaction conditions to produce an olefin polymer, (II)determining a first concentration of the first transition metal compoundand a second concentration of the second transition metal compound in asolution comprising the first transition metal compound and the secondtransition metal compound, and (III) adjusting a first flow rate of thefirst transition metal compound and/or a second flow rate of secondtransition metal compound into the reactor when the first concentrationand/or the second concentration has reached a predetermined level (oradjusting the first flow rate of the first transition metal compoundbased on the first determined concentration and/or adjusting the secondflow rate of the second transition metal compound based on the seconddetermined concentration). The first concentration and the secondconcentration can be determined by any methodology disclosed herein.

Additionally, various polymerization reactor systems are disclosedherein. One such polymerization reactor system can comprise (A) areactor configured to contact a catalyst system with an olefin monomerand an optional olefin comonomer under polymerization reactionconditions to produce an olefin polymer, (B) a catalyst preparationvessel configured to contact a first transition metal compound, a secondtransition metal compound, an activator, and an optional co-catalyst toform the catalyst system, and (C) an analytical system configured todetermine a first concentration of the first transition metal compoundand a second concentration of the second transition metal compound in asolution comprising the first transition metal compound and the secondtransition metal compound present within the polymerization reactorsystem. Consistent with particular aspects of this invention, theanalytical system can comprise an ultraviolet-visible spectrometer.

Both the foregoing summary and the following detailed descriptionprovide examples and are explanatory only. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Further, features or variations may be provided inaddition to those set forth herein. For example, certain aspects may bedirected to various feature combinations and sub-combinations describedin the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

The following figures form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention can be better understood by reference to one ormore of these figures in combination with the detailed description ofspecific aspects presented herein.

FIG. 1 illustrates a schematic block diagram of a polymerization reactorsystem consistent with aspects of this invention.

FIG. 2 presents plots of the UV-Vis absorbance profiles as a function ofwavelength for various concentrations of transition metal compound MET-2in toluene.

FIG. 3 presents linear calibration curves correlating absorbance to theconcentration of transition metal compound MET-2 in toluene at variouswavelengths.

FIG. 4 presents plots of the UV-Vis absorbance profiles as a function ofwavelength for various concentrations of transition metal compound MET-2in 1-hexene.

FIG. 5 presents linear calibration curves correlating absorbance to theconcentration of transition metal compound MET-2 in 1-hexene at variouswavelengths.

FIG. 6 presents plots of the UV-Vis absorbance profiles as a function ofwavelength for various concentrations of transition metal compound MET-1in toluene.

FIG. 7 presents linear calibration curves correlating absorbance to theconcentration of transition metal compound MET-1 in toluene at variouswavelengths.

FIG. 8 presents plots of the UV-Vis absorbance profiles as a function ofwavelength for various concentrations of transition metal compound MET-1in 1-hexene.

FIG. 9 presents linear calibration curves correlating absorbance to theconcentration of transition metal compound MET-1 in 1-hexene at variouswavelengths.

FIG. 10 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, and a mixture of MET-1 and MET-2, in1-hexene/toluene, and a fitted model curve, for Example 1.

FIG. 11 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, and a mixture of MET-1 and MET-2, in1-hexene/toluene, and a fitted model curve, for Example 2.

FIG. 12 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, and a mixture of MET-1 and MET-2, in1-hexene/toluene, and a fitted model curve, for Example 3.

FIG. 13 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, and a mixture of MET-1 and MET-2, in1-hexene/toluene, and a fitted model curve, for Example 4.

FIG. 14 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, MET-3, and a mixture of MET-1, MET-2,and MET-3 in 1-hexene/toluene, and a fitted model curve, for Example 5.

FIG. 15 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, MET-3, and a mixture of MET-1, MET-2,and MET-3 in 1-hexene/toluene, and a fitted model curve, for Example 6.

FIG. 16 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, MET-3, and a mixture of MET-1, MET-2,and MET-3 in 1-hexene/toluene, and a fitted model curve, for Example 7.

FIG. 17 presents plots of the UV-Vis absorbance profiles as a functionof wavelength for MET-1, MET-2, MET-3, and a mixture of MET-1, MET-2,and MET-3 in 1-hexene/toluene, and a fitted model curve, for Example 8.

DEFINITIONS

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2^(nd) Ed (1997), can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Herein, features of the subject matter are described such that, withinparticular aspects, a combination of different features can beenvisioned. For each and every aspect and/or feature disclosed herein,all combinations that do not detrimentally affect the systems,compositions, processes, and/or methods described herein arecontemplated with or without explicit description of the particularcombination. Additionally, unless explicitly recited otherwise, anyaspect and/or feature disclosed herein can be combined to describeinventive features consistent with the present disclosure.

Unless explicitly stated otherwise in defined circumstances, allpercentages, parts, ratios, and like amounts used herein are defined byweight.

In this disclosure, while systems, processes, and methods are oftendescribed in terms of “comprising” various components, devices, orsteps, the systems, processes, and methods can also “consist essentiallyof” or “consist of” the various components, devices, or steps, unlessstated otherwise.

The terms “a,” “an,” and “the” are intended to include pluralalternatives, e.g., at least one. For instance, the disclosure of “apolymerization reactor,” “a transition metal compound,” or “awavelength,” is meant to encompass one, or mixtures or combinations ofmore than one, polymerization reactor, transition metal compound, orwavelength, unless otherwise specified.

For any particular compound or group disclosed herein, any name orstructure (general or specific) presented is intended to encompass allconformational isomers, regioisomers, stereoisomers, and mixturesthereof that can arise from a particular set of substituents, unlessotherwise specified. The name or structure (general or specific) alsoencompasses all enantiomers, diastereomers, and other optical isomers(if there are any) whether in enantiomeric or racemic forms, as well asmixtures of stereoisomers, as would be recognized by a skilled artisan,unless otherwise specified. For instance, a general reference to pentaneincludes n-pentane, 2-methyl-butane, and 2,2-dimethylpropane; and ageneral reference to a butyl group includes a n-butyl group, a sec-butylgroup, an iso-butyl group, and a t-butyl group.

The term “about” means that amounts, sizes, formulations, parameters,and other quantities and characteristics are not and need not be exact,but can be approximate and/or larger or smaller, as desired, reflectingtolerances, conversion factors, rounding off, measurement errors, andthe like, and other factors known to those of skill in the art. Ingeneral, an amount, size, formulation, parameter or other quantity orcharacteristic is “about” or “approximate” whether or not expresslystated to be such. The term “about” also encompasses amounts that differdue to different equilibrium conditions for a composition resulting froma particular initial mixture. Whether or not modified by the term“about,” the claims include equivalents to the quantities. The term“about” can mean within 10% of the reported numerical value, preferablywithin 5% of the reported numerical value.

Various numerical ranges are disclosed herein. When a range of any typeis disclosed or claimed, the intent is to disclose or claim individuallyeach possible number that such a range could reasonably encompass,including end points of the range as well as any sub-ranges andcombinations of sub-ranges encompassed therein, unless otherwisespecified. As a representative example, the present disclosure recitesthat the polymerization reaction conditions can comprise apolymerization reaction temperature in a range from about 60° C. toabout 115° C. in certain aspects. By a disclosure that the temperaturecan be in a range from about 60° C. to about 115° C., the intent is torecite that the temperature can be any temperature within the range and,for example, can be equal to about 60° C., about 65° C., about 70° C.,about 75° C., about 80° C., about 85° C., about 90° C., about 95° C.,about 100° C., about 105° C., about 110° C., or about 115° C.Additionally, the temperature can be within any range from about 60° C.to about 115° C. (for example, the temperature can be in a range fromabout 70° C. to about 110° C.), and this also includes any combinationof ranges between about 60° C. and about 115° C. Likewise, all otherranges disclosed herein should be interpreted in a manner similar tothis example.

The term “polymer” is used herein generically to include olefinhomopolymers, copolymers, terpolymers, and the like, as well as alloysand blends thereof. The term “polymer” also includes impact, block,graft, random, and alternating copolymers. A copolymer can be derivedfrom an olefin monomer and one olefin comonomer, while a terpolymer canbe derived from an olefin monomer and two olefin comonomers.Accordingly, “polymer” encompasses copolymers and terpolymers.Similarly, the scope of the term “polymerization” includeshomopolymerization, copolymerization, and terpolymerization. Therefore,an ethylene polymer would include ethylene homopolymers, ethylenecopolymers (e.g., ethylene/α-olefin copolymers), ethylene terpolymers,and the like, as well as blends or mixtures thereof. Thus, an ethylenepolymer encompasses polymers often referred to in the art as LLDPE(linear low density polyethylene) and HDPE (high density polyethylene).As an example, an ethylene copolymer can be derived from ethylene and acomonomer, such as 1-butene, 1-hexene, or 1-octene. If the monomer andcomonomer were ethylene and 1-hexene, respectively, the resultingpolymer can be categorized an as ethylene/1-hexene copolymer. The term“polymer” also includes all possible geometrical configurations, ifpresent and unless stated otherwise, and such configurations can includeisotactic, syndiotactic, and random symmetries. The term “polymer” alsois meant to include all molecular weight polymers, and is inclusive oflower molecular weight polymers or oligomers. The intent is for the term“polymer” to encompass oligomers (including dimers and trimers) derivedfrom any olefin monomer disclosed herein (as well from an olefin monomerand one olefin comonomer, an olefin monomer and two olefin comonomers,and so forth).

The term “contacting” is used herein to describe systems, compositions,processes, and methods in which the components are contacted or combinedtogether in any order, in any manner, and for any length of time, unlessotherwise specified. For example, the components can be combined byblending or mixing, using any suitable technique.

A “solution” is meant to indicate that there is no visual precipitate atthe conditions (e.g., temperature and pressure) of interest. Forinstance, typical laboratory testing conditions can include atemperature in the 20-25° C. range and a pressure of approximately 1atm. Alternatively, the solution of two of more transition metalcompounds can be tested at elevated temperature and pressure, such as attemperatures and pressures typical of solution polymerization processes,slurry polymerization processes, and the like.

The term “spectrometer” is used herein generically to include devicesthat may be referred to in the art as a spectrometer or aspectrophotometer, and the like.

As used herein, the term “near real-time” refers to a delay that isintroduced by automated data processing between the occurrence of anevent and the use of the processed data. For example, classifying anevent as a near real-time event refers to the real-time eventoccurrence, minus the processing time, as nearly the time of the liveevent. That is, the time interval between when data is received foranalysis and analysis is performed and displayed (e.g., on a computerscreen or alternate device) or an activity is undertaken (e.g.,adjusting a flow rate of the first and/or second transition metalcompound), which is within 1 minute to within 10 minutes, for example, atime interval as short as 3 seconds to 3 minutes.

As used herein, the term “real-time” or “actual real-time” can refer tothe instant capture of a measured item at the time of captureoccurrence, e.g., the instantaneous or nearly instantaneous streaming ortransmission of data or information. The real-time data can be UV-Visanalysis data or sensor reading data that can be provided instantly,such as within 2 seconds, to a computer system, to computer readablemedium, or to a controller, and the like, as soon as the UV-Vis readingis obtained.

Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of theinvention, the typical methods, devices, and materials are hereindescribed.

All publications and patents mentioned herein are incorporated herein byreference for the purpose of describing and disclosing, for example, theconstructs and methodologies that are described in the publications,which might be used in connection with the presently describedinvention.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are methods for determining the respectiveconcentrations of a first transition metal compound and a secondtransition metal compound in solutions containing the first transitionmetal compound and the second transition metal compound, and relatedprocesses for operating polymerization reactor systems. Also disclosedherein are polymerization reactor systems comprising analytical systemsfor determining the respective concentrations of a first transitionmetal compound and a second transition metal compound in solutionscontaining the first transition metal compound and the second transitionmetal compound, and processes for operating such reactor systems. Whilenot wishing to be bound by theory, it is believed that such reactorsystems (and related methods) can offer improved control and/orreal-time monitoring or measurement of the amount of the transitionmetal compounds present in catalyst component feed streams, catalystsystems, and polymerization reactor systems, ultimately resulting inimproved quality control and consistency of the polymerization process.Beneficially, the reactor systems (and related methods) disclosed hereinallow for determining the respective concentrations of the firsttransition metal compound and the second transition metal compound witha single test and with exceptional precision, even where the absorbanceprofiles of the first transition metal compound and the secondtransition metal compound overlap significantly, and/or where one of thefirst and second transition metal compounds is in large excess relativeto the other. Advantageously, the reactor systems (and related methods)disclosed herein can be applied in circumstances where the respectiveabsorbance profiles of the transition metal compounds cannot bedeconvoluted or determined independently. Accordingly, since preciseinformation on the respective concentrations of the first and secondtransition metal compounds can be determined, the polymerization reactorsystems (and related methods) disclosed herein can permit real-timemonitoring, control, adjustment, and/or fine tuning of the respectiveconcentrations of the first and second transition metal compounds withina production run of an individual grade of polymer resin.

Methods for Determining the Concentrations of Transition Metal Compounds

Aspects of this invention are directed to methods for determining afirst concentration of a first transition metal compound and a secondconcentration of a second transition metal compound in a solutioncomprising the first transition metal compound and the second transitionmetal compound. Such methods can comprise (or consist essentially of, orconsist of) (i) providing a first reference absorbance profile (F₁) ofthe first transition metal compound in a first reference solution at afirst known concentration, and a second reference absorbance profile(F₂) of the second transition metal compound in a second referencesolution at a second known concentration, (ii) submitting a sample ofthe solution to a sample chamber, (iii) irradiating the sample in thechamber with a light beam at a wavelength (one or more than one) in theUV-visible spectrum, (iv) generating (e.g., collecting or outputting) asample absorbance profile of the sample, and calculating a curve havingthe formula β₁F₁+β₂F₂ to fit the sample absorbance profile to aleast-squares regression fit value (R²) of at least 0.9, wherein β₁ is afirst weighting coefficient, F₁ is the first reference absorbanceprofile of the first transition metal compound in the first referencesolution at the first known concentration, β₂ is a second weightingcoefficient, and F₂ is the second reference absorbance profile of thesecond transition metal compound in the second reference solution at thesecond known concentration, and (v) multiplying the first knownconcentration with β₁ to determine the first concentration of the firsttransition metal compound in the solution, and multiplying the secondknown concentration with β₂ to determine the second concentration of thesecond transition metal compound in the solution.

Generally, the features of the methods disclosed herein (e.g., thetransition metal compounds, the solution, the wavelength(s) of the lightbeam, the absorbance profiles, and the curve, among others) areindependently described herein, and these features can be combined inany combination to further describe the disclosed methods. Moreover,other process steps can be conducted before, during, and/or after any ofthe steps listed in the disclosed methods, unless stated otherwise.

In step (i), a first reference absorbance profile (F₁) of the firsttransition metal compound in a first reference solution at a first knownconcentration, and a second reference absorbance profile (F₂) of thesecond transition metal compound in a second reference solution at asecond known concentration are provided. The first reference solutionand the second reference solution can contain the first transition metalcompound and the second transition metal compound, respectively, at anysuitable concentration, and can contain any suitable solvent. Likewise,the solution is not limited to the respective concentrations of thefirst transition metal compound and the second transition metal compoundin the solution, and is not limited to any particular solvent.

Generally, the solution comprises the first transition metal compound,the second transition metal compound, and a hydrocarbon solvent,although the methods disclosed herein can be employed for other solventtypes, such as chlorinated hydrocarbons, ethers, alcohols, and so forth.Typical hydrocarbon solvents can include, but are not limited to,propane, cyclohexane, cyclohexene, isobutane, n-butane, n-pentane,isopentane, neopentane, n-hexane, 1-hexene, toluene, and the like, aswell as combinations thereof. Other suitable hydrocarbon solvents caninclude the ISOPAR® family of mixed aliphatic hydrocarbon solvents, suchas, for example, ISOPAR® C, ISOPAR® E, ISOPAR® G, ISOPAR® H, ISOPAR® L,ISOPAR® M, and the like, as well as mixtures thereof. While not wishingto be bound by theory, it is believed that the type of transition metalcompounds and the type of solvent present in the solution can impact thewavelength or wavelengths to be utilized in the systems andmethods/processes disclosed herein. In particular aspects of thisinvention, the systems and methods/processes disclosed herein are wellsuited for determining the respective concentrations of the firsttransition metal compound and the second transition metal compound in asolution containing the first transition metal compound, a secondtransition metal compound, and a hydrocarbon solvent. The hydrocarbonsolvent can comprise, for instance, 1-hexene, isobutane, toluene, orcyclohexene, and the like, as well as mixtures or combinations thereof.

In one aspect, the solution (containing the first transition metalcompound and the second transition metal compound), the first referencesolution, and the second reference solution can comprise the samesolvent (e.g., the same hydrocarbon solvent), while in another aspect,at least two of the solution (containing the first transition metalcompound and the second transition metal compound), the first referencesolution, and the second reference solution can comprise a differentsolvent (e.g., a different hydrocarbon solvent).

The selection of the solvent can affect the absorbance profiles ofcertain transition metal compounds. Thus, it can be beneficial for thefirst reference solution and the second reference solution to containthe same solvent as that of the solution (containing the firsttransition metal compound and the second transition metal compound). Insuch aspects, any solvent effects can be minimized, leading to improvedaccuracy in determining the respective concentrations of the firsttransition metal compound and the second transition metal compound.

Any of the absorbance profiles described herein (e.g., the sampleabsorbance profile, the first reference absorbance profile (F₁), and thesecond reference absorbance profile (F₂)) can comprise an absorbancepeak at a single wavelength in some aspects of this invention.Alternatively, any absorbance profiles described herein can comprise anabsorbance curve (peaks and/or areas under curves as a function ofwavelength) over a range of wavelengths, such as from 200 nm to 750 nm,or from 300 nm to 600 nm, and so forth. Thus, data from the respectiveabsorbance curves over a range of wavelengths can be used fordetermining the respective concentrations of the first transition metalcompound and the second transition metal compound in the solution.Additionally or alternatively, any absorbance profiles described hereincan comprise an absorbance curve (peaks and/or areas under curves as afunction of wavelength) over a subset of wavelengths spanning less than350 nm, less than 300 nm, less than 250 nm, less than 200 nm, or lessthan 150 nm. Thus, data from the respective absorbance curves over aspecific subset of wavelengths ranges can be used for determining therespective concentrations of the first transition metal compound and thesecond transition metal compound in the solution. Other suitableabsorbance profile options are readily apparent from this disclosure.

Generally, the path lengths used for the first reference absorbanceprofile (F₁), the second reference absorbance profile (F₂), and thesample absorbance profile often can be the same, although this is not arequirement

In step (ii), a sample of the solution containing the first and secondtransition metal compounds (at least two transition metal compounds) issubmitted to a sample chamber. The sample chamber can be a flow cell,although any suitable design and configuration of the sample chamber canbe used. In further aspects, the solution can contain more than twodifferent transition metal compounds. Accordingly, the solutioncontaining the transition metal compounds can contain two differenttransition metal compounds, or more than two different transition metalcompounds. As a non-limiting example, the solution can contain twometallocene compounds: one bridged metallocene compound and oneunbridged metallocene compound, two different bridged metallocenecompounds, or two different unbridged metallocene compounds.

The sample in the sample chamber can be irradiated with a light beam ata wavelength in the UV-visible spectrum in step (iii). Such can beaccomplished, for instance, by a UV-Vis spectrometer, discussedhereinbelow. The wavelength of the light beam can be a singlewavelength, or more than one wavelength, such as a range of wavelengths(e.g., a 200 nm wavelength range or a 300 nm wavelength range). In oneaspect, the wavelength of the light beam can comprise wavelengths in thevisible spectrum (from 380 nm to 780 nm). In another aspect, thewavelength of the light beam can comprise wavelengths in the 200 nm to750 nm range. Yet, in another aspect, the wavelength of the light beamcan comprise wavelengths in the 300 nm to 600 nm range. Thus, anysuitable wavelength range can be employed depending upon, for instance,the specific transition metal compounds or the specific hydrocarbonsolvent. Often, step (iii) can be performed in the 300-600 nm wavelengthrange. Moreover, if desired, the UV-Vis light/radiation can be filteredin some aspects of this invention.

In step (iv), a sample absorbance profile of the sample, which containsa solution of the first and second transition metal compounds, isgenerated. Then, a curve having the formula β₁F₁+β₂F₂ can be calculatedto fit the sample absorbance profile to a least-squares regression fitvalue (R²) of at least 0.9. In the curve having the formula β₁F₁+β₂F₂,β₁ is a first weighting coefficient, F₁ is the first referenceabsorbance profile of the first transition metal compound in the firstreference solution at the first known concentration, β₂ is a secondweighting coefficient, and F₂ is the second reference absorbance profileof the second transition metal compound in the second reference solutionat the second known concentration.

While not limited thereto, the curve having the formula β₁F₁+β₂F₂ can bedetermined (and, thus, the first weighting coefficient (β₁) and thesecond weighting coefficient (β₂) can be determined) over any suitablerange of wavelengths to fit the sample absorbance profile. For instance,the range of wavelengths can be from 200 nm to 750 nm; alternatively,from 300 nm to 600 nm; alternatively, from 350 nm to 600 nm; oralternatively, from 350 nm to 550 nm. Additionally or alternatively, thecurve having the formula β₁F₁+β₂F₂ can be determined (and, thus, thefirst weighting coefficient (β₁) and the second weighting coefficient(β₂) can be determined) over any suitable subset of wavelengths to fitthe sample absorbance profile. For instance, the subset of wavelengthscan span less than 350 nm, less than 300 nm, less than 250 nm, less than200 nm, or less than 100 nm. Hence, in particular aspects of thisinvention, the curve having the formula β₁F₁+β₂F₂ can be determined(and, thus, the first weighting coefficient (β₁) and the secondweighting coefficient (β₂) can be determined) over a subset ofwavelengths spanning less than 350 nm, less than 300 nm, less than 250nm, less than 200 nm, or less than 100 nm, in the 200 nm to 750 nmwavelength range, or in the 300 nm to 600 nm wavelength range, to fitthe sample absorbance profile. Other wavelength options are readilyapparent from this disclosure.

While not being limited thereto, in some aspects of this invention, thegenerating and calculating operations in step (iv), independently, canbe conducted over a broad spectrum of wavelengths, such as in the300-600 nm range, and the first reference and second referenceabsorbance profiles, independently, can be conducted over the same or adifferent spectrum of wavelengths, such as in the 300-600 nm range, butnot limited thereto.

Using the techniques disclosed herein can result in the curve having theformula β₁F₁+β₂F₂ providing an excellent fit to the sample absorbanceprofile, with a least-squares regression fit value (R²) of at least 0.9,and more often, at least 0.95, or at least 0.98. In many instances, thecurve and the sample absorbance profile overlap so completely that theplots cannot be distinguished. Thus, least-squares regression fit values(R²) of at least 0.99, of at least 0.999, or of at least 0.9995, can bereadily achieved.

In step (v), the first known concentration and β₁ are multiplied todetermine the first concentration of the first transition metal compoundin the solution, and the second known concentration and β₂ aremultiplied to determine the second concentration of the secondtransition metal compound in the solution.

In some instances, actual absorbance profiles (sample, first reference,second reference) can be generated, which can be collected or outputted,such as in the form of a plot of the absorbance as a function of thewavelength, which can be viewed on a monitor or computer screen, orprinted in hard copy form. In other instances, the absorbance profilesare generated, but not collected or outputted into a viewable form. Forexample, data from the sample absorbance profile, the first referenceabsorbance profile, and the second absorbance profile—e.g., absorbanceas a function of the wavelength—can be used to directly determine thefirst weighting coefficient (β₁) and the second weighting coefficient(β₂), for subsequent conversion to the respective concentrations of thefirst and second transition metal concentrations.

The step of calculating the curve having the formula β₁F₁+β₂F₂ cancomprise any suitable method or technique that fits the sampleabsorbance profile—whether from a narrow subset of wavelength ranges orfrom a broad spectrum of wavelengths—and determines the first weightingcoefficient (β₁) and the second weighting coefficient (β₂), forsubsequent conversion to the respective concentrations of the first andsecond transition metal concentrations. These steps can be performedmanually, or can be configured to automatically determine the respectiveconcentrations of the first and second transition metal compounds oncethe sample absorbance profile has been generated. Thus, steps (iv) and(v) can be performed sequentially or simultaneously, and can beperformed manually or can be computerized (e.g., for automaticdetermination of the respective concentrations of the first and secondtransition metal compounds in the solution).

Generally, the respective concentrations of the first and secondtransition metal compounds in the first and second reference solutionsare not limited to any particular range. However, in certain aspects,the first known concentration of the first transition metal compound inthe first reference solution can be such that the absorbance peak at asingle wavelength in the first reference absorbance profile (forinstance, the absorbance peak at 380 nm) can be less than 2, less than1, or less than 0.5. In particular aspects, the first knownconcentration of the first transition metal compound in the firstreference solution can be such that the absorbance peak at a singlewavelength in the first reference absorbance profile can be in a rangefrom about 0.1 to about 2, from about 0.1 to about 1, from about 0.3 toabout 1, or from about 0.5 to about 1. These same concentration andabsorbance ranges can apply to second transition metal compound in thesecond reference solution.

Likewise, the respective concentrations of the first and secondtransition metal compound in the solution are not limited to anyparticular range. For instance, the concentration of the firsttransition metal compound in the solution and the concentration of thesecond transition metal compound in the solution, independently, can beless than about 5 wt. %, less than about 2 wt. %, less than about 1 wt.%, less than about 0.8 wt. %, less than about 0.5 wt. %, less than about0.2 wt. %, less than about 0.1 wt. %, less than about 0.05 wt. %, orless than about 0.01 wt. %. Illustrative and non-limiting ranges for theconcentration of the first transition metal compound in the solution andthe concentration of the second transition metal compound in thesolution, independently, can include from about 0.01 wt. % to about 5wt. %, from about 0.01 wt. % to about 1 wt. %, from about 0.01 wt. % toabout 0.5 wt. %, from about 0.05 to about 0.2 wt. %, from about 0.01 wt.% to about 0.1 wt. %, or from about 0.1 wt. % to about 0.3 wt. %.

Alternatively, or in addition to, determining the absolute concentrationof the first transition metal compound and the second transition metalcompound, the methods described herein can be used to determine therelative concentrations (or relative amounts) of the first and secondtransition metal compounds. In certain aspects, the weight ratio of thefirst transition metal compound to the second transition metal compound(first:second) in the solution can be less than about 1:1, less thanabout 1:4, less than about 1:10, or less than about 1:20. In otheraspects, the weight ratio of the first transition metal compound to thesecond transition metal compound in the solution can be in a range fromabout 50:1 to about 1:50, from about 10:1 to about 1:10, from about 2:1to about 1:2, from about 1:20 to about 1:1, from about 1:100 to about1:2, from about 1:50 to about 1:5, from about 1:50 to about 1:10, orfrom about 1:20 to about 1:10.

The methods disclosed herein are applicable to a wide variety ofcircumstances where the concentrations of transition metal compounds ina solution (or a mixture, from which a solution can be derived) may beof interest. In one aspect, the solution comprising the first and secondtransition metal compounds can be a feed stream to a catalystpreparation vessel. The catalyst preparation vessel can be any vessel orapparatus that is capable of contacting (e.g., mixing or blending) twoor more components of a catalyst system to form a catalyst system. Anytwo or more components can be precontacted for a suitable period of timeperiod prior to contacting with the remaining components to form thefinished catalyst system, which can then be transferred from thecatalyst preparation vessel to the reactor, as needed. Often, in thecatalyst preparation vessel, the transition metal compounds (two ormore) and an activator (one or more) are contacted, or alternatively,the transition metal compounds (two or more), an activator (one ormore), and a co-catalyst are contacted, to form the catalyst system.

In another aspect, the solution comprising the first and secondtransition metal compounds can be a liquid (or homogeneous) catalystsystem comprising the transition metal compounds. The catalyst systemcan contain, in addition to the transition metal compounds, componentsincluding a liquid activator (or a solution of a liquid activator), suchas MAO, as well as a liquid co-catalyst (or a solution of aco-catalyst), if desired in the catalyst system.

In yet another aspect, the solution comprising the first and secondtransition metal compounds can be a solution from a polymerizationreactor (e.g., a solution reactor or slurry reactor) in which the solidsor particulates from a sample stream (of a mixture from the reactor)have been removed, such as via sieving, filtering, centrifuging, and thelike, and including combinations or two or more of these techniques, aswell as any other suitable technique for removing solids or particulatesfrom a mixture to result in a solution. Therefore, in this aspect, thesolution comprising the first transition metal compound and the secondtransition metal compound can be a solution prepared from a samplemixture from a polymerization reactor.

In still another aspect, the solution comprising the first and secondtransition metal compounds can be a solution from a heterogeneous orsupported catalyst system stream, in which the solids or particulatesfrom a sample stream (of the catalyst system mixture) have been removedby any suitable technique, or any technique disclosed herein. Therefore,in this aspect, the solution comprising the first transition metalcompound and the second transition metal compound can be a solutionprepared from a sample mixture of a heterogeneous catalyst system, suchas from a catalyst preparation vessel.

Polymerization Reactor Systems

Various polymerization reactor systems and processes for operating orcontrolling such systems are disclosed and described herein. Forinstance, in one aspect, a process for operating a polymerizationreactor system can comprise (I) contacting a catalyst system comprisinga first transition metal compound, a second transition metal compound,an activator, and an optional co-catalyst, with an olefin monomer and anoptional olefin comonomer in a reactor within the polymerization reactorsystem under polymerization reaction conditions to produce an olefinpolymer, (II) determining a first concentration of the first transitionmetal compound and a second concentration of the second transition metalcompound in a solution comprising the first transition metal compoundand the second transition metal compound, the first concentration andthe second concentration determined via the methods described herein,and (III) adjusting a first flow rate of the first transition metalcompound and/or a second flow rate of second transition metal compoundinto the reactor when the first concentration and/or the secondconcentration has reached a predetermined level. Hence, the first flowrate (or feed rate) of the first transition metal compound can beadjusted, manually and/or automatically, based on the first determinedconcentration, and/or the second flow rate (or feed rate) of the secondtransition metal compound can be adjusted, manually and/orautomatically, based on the second determined concentration. Generally,the features of the processes for operating polymerization reactorsystems disclosed herein (e.g., the transition metal compounds, thecatalyst system, the olefin monomer, the olefin comonomer, the reactor,the method of determining the respective concentrations of the first andsecond transition metal compounds, and the flow rate control of thefirst and second transition metal compounds, among others) areindependently described herein, and can be combined in any combinationto further describe the disclosed processes. Moreover, other steps canbe conducted before, during, and/or after any of the steps listed in thedisclosed processes, unless stated otherwise.

Step (II) is directed to determining a first concentration of the firsttransition metal compound and a second concentration of the secondtransition metal compound in a solution comprising the first transitionmetal compound and the second transition metal compound. Step (II) cancomprise the steps of (i) providing a first reference absorbance profile(F₁) of the first transition metal compound in a first referencesolution at a first known concentration, and a second referenceabsorbance profile (F₂) of the second transition metal compound in asecond reference solution at a second known concentration, (ii)submitting a sample of the solution to a sample chamber, (iii)irradiating the sample in the chamber with a light beam at a wavelength(one or more than one) in the UV-visible spectrum, (iv) generating(e.g., collecting or outputting) a sample absorbance profile of thesample, and calculating a curve having the formula β₁F₁+β₂F₂ to fit thesample absorbance profile to a least-squares regression fit value (R²)of at least 0.9, wherein β₁ is a first weighting coefficient, F₁ is thefirst reference absorbance profile of the first transition metalcompound in the first reference solution at the first knownconcentration, β₂ is a second weighting coefficient, and F₂ is thesecond reference absorbance profile of the second transition metalcompound in the second reference solution at the second knownconcentration, and (v) multiplying the first known concentration with β₁to determine the first concentration of the first transition metalcompound in the solution, and multiplying the second known concentrationwith β₂ to determine the second concentration of the second transitionmetal compound in the solution. Accordingly, the specific featuresrelating to step (II) can be the same as those disclosed and describedherein as it pertains to methods for determining the respectiveconcentrations of the first and second transition metal compounds in asolution containing the first and second transition metal compounds.

The processes disclosed herein are applicable to a wide variety ofcircumstances where the concentration of a transition metal compound ina solution (or a mixture, from which a solution can be obtained) may beof interest. In one aspect, the solution comprising the first transitionmetal compound and the second transition metal compounds can be a feedstream to a catalyst preparation vessel. In this aspect, the first flowrate and/or the second flow rate into the reactor can be controlled byadjusting a flow rate of a feed stream to the catalyst preparationvessel, and/or by adjusting a relative flow rate (ratio of the flow rateof the first transition metal compound to the flow rate of the secondtransition metal compound—first:second transition metal compound) to thecatalyst preparation vessel, and/or by adjusting a total flow rate ofthe catalyst system exiting the catalyst preparation vessel and enteringthe reactor.

As an example, if the concentration of the first transition metalcompound is below a target concentration, the first flow rate of thefirst transition metal compound into the reactor can be increased byincreasing a relative flow rate (ratio of the flow rate of the firsttransition metal compound to the flow rate of the second transitionmetal compound) to the catalyst preparation vessel. This can beaccomplished, for instance, by increasing the feed rate of the firsttransition metal compound to the catalyst preparation vessel, whilekeeping constant the feed rate of the second transition metal compoundto the catalyst preparation vessel.

As another example, if the concentration of the first transition metalcompound is below a target concentration, the first flow rate of thefirst transition metal compound into the reactor can be increased byincreasing a relative flow rate (ratio of the flow rate of the firsttransition metal compound to the flow rate of the second transitionmetal compound) to the reactor. This can be accomplished, for instance,by increasing the first flow rate of the first transition metal compoundto the reactor, while keeping constant the second flow rate of thesecond transition metal compound to the reactor.

In another aspect, the catalyst system can be a liquid (or homogeneous)catalyst system, and the solution comprising the first transition metalcompound and the second transition metal compound can be a sample of theliquid catalyst system. In this aspect, the first flow rate and/or thesecond flow rate can be controlled by adjusting a relative flow rate(ratio of the first flow rate of the first transition metal compound tothe second flow rate of the second transition metal compound) to thereactor, and/or by adjusting a total flow rate of the liquid catalystsystem entering the reactor.

In yet another aspect, the polymerization reactor system comprises apolymerization reactor (e.g., a solution polymerization reactor or aslurry polymerization reactor), and the solution comprising the firsttransition metal compound and the second transition metal compound canbe a solution prepared from a sample of the mixture from thepolymerization reactor. In this aspect, the first flow rate and/or thesecond flow rate can be controlled by adjusting a relative flow rate(ratio of the first flow rate of the first transition metal compound tothe second flow rate of the second transition metal compound) to thereactor, and/or by adjusting a total flow rate of the catalyst systementering the polymerization reactor. The solids or particulates from thesample of the mixture from the polymerization reactor can be removed byany suitable technique. Optionally, cooling the sample of the mixturecan be beneficial. This process can be useful for determining therespective amounts of the first and second transition metal compoundsthat are not impregnated in, on, or associated with any solid catalystcomponents and/or polymer particulates, e.g., to determine therespective amounts (or percentages) of the first and second transitionmetal compounds that are present in solution.

In still another aspect, the catalyst system can be a heterogeneous orsupported catalyst system, and the solution comprising the firsttransition metal compound and the second transition metal compound canbe a solution obtained from a sample stream of the heterogeneous orsupported catalyst system. In this aspect, the first flow rate and/orthe second flow rate can be controlled by adjusting a relative flow rate(ratio of the first flow rate of the first transition metal compound tothe second flow rate of the second transition metal compound) to thereactor, and/or by adjusting a total flow rate of the catalyst systementering the polymerization reactor. As above, this process can beuseful in determining the respective amounts of the first and secondtransition metal compounds that are not impregnated in, on, orassociated with the solid catalyst components of the catalyst system,e.g., to determine the respective amounts (or percentages) of the firstand second transition metal compounds that are present in solution.

Consistent with aspects disclosed herein, in step (III), when the firstconcentration and/or the second concentration in the solution hasreached a predetermined level, the first flow rate of the firsttransition metal compound and/or the second flow rate of secondtransition metal compound into the reactor can be adjusted. Thepredetermined level can be readily ascertained by one of skill in theart depending upon, for instance, the historic and the prevailingconditions in the polymerization reactor system. As non-limitingexamples, a predetermined level can be a decrease of a certainpercentage of the first concentration of the first transition metalcompound (e.g., beyond that which is deemed allowable during normalon-prime production), or the increase of a certain percentage of thefirst concentration of the first transition metal compound in thesolution (e.g., beyond which is deemed allowable during normal on-primeproduction). For instance, the target concentration of the firsttransition metal compound in the solution can be 0.1 wt. %, and thepredetermined lower and upper control limits can be 0.09 wt. % and 0.11wt. %, respectively, for normal on-prime production. If the measuredfirst concentration of the first transition metal compound in thesolution was 0.08 wt. %, then the feed rate of the first transitionmetal compound to the catalyst preparation vessel (and in turn, thefirst flow rate to the polymerization reactor) can be increased to bringthe concentration of the first transition metal compound to anacceptable level within the predetermined limits of 0.09-0.11 wt. %.Conversely, if the concentration of the first transition metal in thesolution was too high (e.g., 0.12+wt. %), then the first flow rate ofthe first transition metal compound can be decreased to bring theconcentration to an acceptable level within the predetermined limits. Inlike manner, if the second concentration of the second transition metalcompound in the solution has reached a predetermined level, similaradjustments can be made to the second flow rate of second transitionmetal compound into the reactor as needed.

In another aspect of this invention, a polymerization reactor system isprovided, and in this aspect, the polymerization reactor system cancomprise (A) a reactor configured to contact a catalyst system with anolefin monomer and an optional olefin comonomer under polymerizationreaction conditions to produce an olefin polymer, (B) a catalystpreparation vessel configured to contact a first transition metalcompound, a second transition metal compound, an activator, and anoptional co-catalyst to form the catalyst system, and (C) an analyticalsystem configured to determine a first concentration of the firsttransition metal compound and a second concentration of the secondtransition metal compound in a solution comprising the first transitionmetal compound and the second transition metal compound present withinthe polymerization reactor system. Generally, the features of any of thepolymerization reactor systems disclosed herein (e.g., thepolymerization reactor, the catalyst system, the olefin monomer (andolefin comonomer, if any), the polymerization conditions, the olefinpolymer, the catalyst preparation vessel, the analytical system, amongothers) are independently described herein, and these features can becombined in any combination to further describe the disclosedpolymerization reactor systems. Moreover, other devices or reactorsystem components in addition to the reactor, the catalyst preparationvessel, and the analytical system, can be present in the disclosedpolymerization reactor systems, unless stated otherwise. Additionally,the catalyst system can be contacted with an olefin monomer and anolefin comonomer (e.g., contacted with ethylene and an α-olefincomonomer, such as 1-hexene) in the polymerization reactor in certainaspects contemplated herein.

The analytical system (C) can include any analytical system or devicethat is capable of determining a first concentration of the firsttransition metal compound and a second concentration of the secondtransition metal compound in a solution that contains both the firsttransition metal compound and the second transition metal compound. Forinstance, the analytical system can include an ultraviolet-visible(UV-Vis) spectrometer (e.g., alone or in combination with anotheranalytical device/method, such as a fluorescence spectroscopy method; aUV-Vis-NIR system; and so forth). In one aspect of this invention, theanalytical system can include an ultraviolet-visible spectrometer withan integrated computer system, such that the spectrometer and integratedcomputer system are capable of measuring (or configured to measure) asample absorbance profile of the solution; capable of calculating (orconfigured to calculate) a curve having the formula β₁F₁+β₂F₂ to fit thesample absorbance profile to a least-squares regression fit value (R²)of at least 0.9, wherein β₁ is a first weighting coefficient, F₁ is afirst reference absorbance profile of the first transition metalcompound in a first reference solution at a first known concentration,β₂ is a second weighting coefficient, and F₂ is a second referenceabsorbance profile of the second transition metal compound in a secondreference solution at a second known concentration; and capable ofmultiplying (or configured to multiply) the first known concentrationwith β₁ to determine the first concentration of the first transitionmetal compound in the solution, and multiplying the second knownconcentration with β₂ to determine the second concentration of thesecond transition metal compound in the solution. In this aspect, theUV-Vis spectrometer has a “built-in” computer system, performing theabsorbance measurements and subsequent calculations to convert theabsorbance data into the respective concentrations of the first andsecond transition metal compounds. In further aspects, the UV-Visspectrometer and integrated computer can be capable of storing referenceabsorbance profiles, such as F₁ (the first reference absorbance profileof the first transition metal compound in a first reference solution ata first known concentration) and F₂ (the second reference absorbanceprofile of the second transition metal compound in a second referencesolution at a second known concentration).

In another aspect of this invention, the analytical system can includean ultraviolet-visible spectrometer and an external computer system,such that the ultraviolet-visible spectrometer is capable of measuring(or configured to measure) a sample absorbance profile of the solution,and the external computer system is capable of calculating (orconfigured to calculate) a curve having the formula β₁F₁+β₂F₂ to fit thesample absorbance profile to a least-squares regression fit value (R²)of at least 0.9, and capable of multiplying (or configured to multiply)the first known concentration with β₁ to determine the firstconcentration of the first transition metal compound in the solution,and multiplying the second known concentration with β₂ to determine thesecond concentration of the second transition metal compound in thesolution. In this aspect, the UV-Vis can perform the absorbancemeasurement of the solution and generate the absorbance data andprofile, but an external computer system can take the output from theUV-Vis and determine the respective concentrations of the first andsecond transition metal compounds.

If desired, the analytical system can further comprise a filter assemblydesigned to filter the sample of the solution containing the first andsecond transition metal compounds before analysis by the UV-Visspectrometer.

As described herein, the absorbance profiles (e.g., the sampleabsorbance profile, the first reference absorbance profile, and thesecond reference absorbance profile) independently can comprise anabsorbance peak at a single wavelength in some aspects of thisinvention. Additionally or alternatively, the absorbance profilesindependently can comprise an absorbance curve (peaks and/or areas undercurves, as a function of wavelength) over a range of wavelengths, suchas from 200 nm to 750 nm, or from 300 nm to 600 nm, and so forth. Thus,data from an absorbance curve over the range of wavelengths can be usedfor determining the respective concentrations of the first and secondtransition metal compounds in the solution. Additionally oralternatively, the absorbance profiles independently can comprise anabsorbance curve (peaks and/or areas under curves, as a function ofwavelength) over a subset of wavelengths spanning less than 350 nm, lessthan 300 nm, less than 250 nm, less than 200 nm, or less than 150 nm.Thus, data from the absorbance curves over a specific subset ofwavelengths ranges can be used for determining the respectiveconcentrations of the first and second transition metal compounds in thesolution. Other suitable absorbance profile options and combinations arereadily apparent from this disclosure.

For example, and while not being limited thereto, the sample absorbanceprofile can be generated and the curve having the formula β₁F₁+β₂F₂ tofit the sample absorbance profile can be generated, independently, overany suitable wavelength range, such as in the 300-600 nm range or asubset thereof, and the first reference and second reference absorbanceprofiles, independently, can be conducted over the same or a differentspectrum of wavelengths, such as in the 300-600 nm range or a subsetthereof, but not limited thereto.

The analytical system and techniques disclosed herein can result in thecurve having the formula β₁F₁+β₂F₂ providing an excellent fit to thesample absorbance profile, with a least-squares regression fit value(R²) of at least 0.9, and more often, at least 0.95, or at least 0.98.In many instances, the curve and the sample absorbance profile overlapso completely that the plots cannot be distinguished. Thus,least-squares regression fit values (R²) of at least 0.99, of at least0.999, or of at least 0.9995, can be readily achieved.

The catalyst preparation vessel (B) in the polymerization reactor systemcan include any vessel or apparatus that is capable of contacting (e.g.,mixing or blending) two or more components of a catalyst system to formthe catalyst system. The catalyst preparation vessel can be a mixingtank or other suitable stirred tank or vessel. The catalyst system canbe delivered from the catalyst preparation vessel to the reactor, asneeded. Often, in the catalyst preparation vessel, the transition metalcompounds (two or more) and an activator (one or more) are contacted, oralternatively, the transition metal compounds (two or more), anactivator (one or more), and a co-catalyst are contacted, to form thecatalyst system. Multi-component catalyst preparation vessels andmethods are disclosed in, for instance, U.S. Pat. No. 7,615,596 (e.g., apre-contactor), which is incorporated herein by reference in itsentirety.

Optionally, the polymerization reactor system can further comprise acontroller (D) that is capable of controlling (or configured to control)a first flow rate of the first transition metal compound and/or a secondflow rate of second transition metal compound into the reactor based on,or according to, the first concentration and/or the second concentrationdetermined by the analytical system. Thus, the polymerization reactorsystem can comprise a reactor, a catalyst preparation vessel, ananalytical system, and a controller. The controller, which can compriseany suitable processing unit or computer system, can be used to analyzethe data regarding the respective concentrations of the first and secondtransition metal compounds in the solution, and adjust the first flowrate and/or second flow rate into the reactor based on the determinedconcentrations. In another aspect, the controller can be programmed withan algorithm to control the first flow rate and/or the second flow rateinto the reactor based on the concentrations determined by theanalytical system. As an example, if the second concentration determinedby the analytical system is too low, the second flow rate of the secondtransition metal compound into the reactor can be increased by thecontroller. In yet another aspect, the controller operative to controlthe first flow rate and/or the second flow rate can comprise acontroller operative to receive information on the respectiveconcentrations of the first and second transition metal compounds, toidentify new target first and/or transition metal compoundconcentrations (e.g., increase or decrease the first flow rate and/orsecond flow to achieve a desired impact on the first or secondtransition metal compound concentration), and to provide a controlsignal to adjust the first flow rate and/or second flow rate into thereactor system accordingly.

The controller can be operated on an as-needed basis, at set timeintervals, or continuously, depending upon the requirements of thereactor system. Thus, it is contemplated that the respectiveconcentrations of the first and second transition metal compounds can bemonitored and/or adjusted and/or controlled continuously. Accordingly,in particular aspects consistent with this invention, the polymerizationreactor system and the controller can operate in real-time or nearreal-time, such that the respective concentrations of the first andsecond transition metal compounds can be determined, and that determinedconcentrations can be used, instantaneously or nearly instantaneously,to adjust the first flow rate of the first transition metal compoundand/or the second flow rate of the second transition metal compound intothe reactor.

The controller or computing device can be implemented using a personalcomputer, a network computer, a server, a mainframe, or other similarmicrocomputer-based workstation. The controller or computing device cancomprise any computer operating environment, such as hand-held devices,multiprocessor systems, microprocessor-based or programmable senderelectronic devices, minicomputers, mainframe computers, and the like.The controller or computing device also can be practiced in distributedcomputing environments where tasks are performed by remote processingdevices. Furthermore, the controller or computing device can comprise amobile terminal, such as a smart phone, a cellular telephone, a cellulartelephone utilizing wireless application protocol (WAP), personaldigital assistant (PDA), intelligent pager, portable computer, a handheld computer, a conventional telephone, a wireless fidelity (Wi-Fi)access point, or a facsimile machine. The aforementioned systems anddevices are examples, and the controller or computing device cancomprise other systems or devices. Controller or computing device alsocan be implemented via a system-on-a-chip (SOC) where each and/or manyof the components illustrated above can be integrated onto a singleintegrated circuit. Such an SOC device can include one or moreprocessing units, graphics units, communications units, systemvirtualization units and various application functionalities, all ofwhich can be integrated (or “burned”) onto the chip substrate as asingle integrated circuit. Other controller methodologies and devicesare readily apparent to one of skill in the art in view of thisdisclosure.

Controllers of the systems disclosed herein can control the first flowrate and/or the second flow rate of the first and second transitionmetal compound, respectively, into or within the polymerization reactorsystem by any method that affords precise and near instantaneous controlof the respective concentrations of the first and second transitionmetal compounds.

The systems disclosed herein are applicable to a wide variety ofcircumstances where the respective concentrations of first and secondtransition metal compounds in a solution (or a mixture, from which asolution can be obtained), which contains the first transition metalcompound and a second transition metal compound, may be of interest. Inone aspect, the solution comprising the first transition metal compoundand a second transition metal compound can be a feed stream to thecatalyst preparation vessel. In this aspect, the controller can controlthe first flow rate and/or the second flow rate into the reactor byadjusting a flow rate of the feed stream to the catalyst preparationvessel, and/or by adjusting a relative flow rate of the first and secondtransition metal compounds rate (ratio of first:second transition metalcompound) to the catalyst preparation vessel, and/or by adjusting a flowrate of the catalyst system exiting the catalyst preparation vessel andentering the reactor.

In another aspect, the catalyst system can be a liquid (or homogeneous)catalyst system, and the solution comprising the first and secondtransition metal compounds can be a sample of the liquid catalystsystem. In this aspect, the controller can control the first flow rateand/or the second flow rate into the reactor by adjusting a relativeflow rate of the first and second transition metal compounds to thereactor, and/or by adjusting a flow rate of the liquid catalyst systementering the reactor.

In yet another aspect, the polymerization reactor system can comprise apolymerization reactor (e.g., a solution reactor or a slurry reactor)containing a reaction mixture, and the solution comprising the first andsecond transition metal compounds can be a solution prepared orseparated from a sample stream from the polymerization reactor. In thisaspect, the controller can control the first flow rate and/or the secondflow rate into the reactor by adjusting a relative flow rate of thefirst and second transition metal compounds to the reactor, and/or byadjusting a flow rate of the catalyst system entering the reactor. Asdescribed herein, the solids or particulates from the sample stream(reaction mixture) can be removed by any suitable technique. Optionally,cooling the sample stream can be beneficial. This process can be usefulin determining the respective amounts of the first and second transitionmetal compounds that are not impregnated in, on, or associated with thesolid catalyst components and/or polymer particulates, e.g., todetermine the respective amounts of the first and second transitionmetal compounds (or the fractions thereof) that are present in solution.

In still another aspect, the solution comprising the first and secondtransition metal compounds can be a solution obtained or separated froma sample stream of a heterogeneous or supported catalyst system feedstream. In this aspect, the first flow rate and/or the second flow rateinto the reactor can be controlled by adjusting a relative flow rate tothe reactor, and/or by adjusting a flow rate of the catalyst systementering the reactor. As above, this process can be useful indetermining the respective amounts of the first and second transitionmetal compounds that are not impregnated in, on, or associated with thesolid catalyst components of the catalyst system, e.g., to determine therespective amounts of the first and second transition metal compounds(or fractions thereof) that are present in solution.

A representative polymerization reactor system 100 consistent withaspects of this invention is illustrated in FIG. 1. The polymerizationreactor system 100 includes a catalyst preparation vessel 110, a reactor120, an analytical system 140, and a controller 150. The analyticalsystem 140 can include a UV-Vis spectrometer as described herein. Thepolymerization reactor system 100 of FIG. 1 includes a first transitionmetal compound solution feed stream 102 and a second transition metalcompound solution feed stream 104 which form a combined transition metalcompound solution feed stream 105 to the catalyst preparation vessel(separate feed streams to the catalyst preparation vessel for othercatalyst components are not shown). In other aspects not shown in FIG.1, feed streams 102 and 104 can be independently fed directly to thecatalyst preparation vessel 110 and/or to the reactor 120. As shown inFIG. 1, a sample stream 132 from the combined feed stream 105 can besubmitted to the analytical system 140 for determination of therespective concentrations of the first and second transition metalcompounds in the combined feed stream 105 prior to its entry into thecatalyst preparation vessel 110.

The polymerization reactor system 100 includes a catalyst system feedstream 115 from the catalyst preparation vessel 110 to the reactor 120.The catalyst system feed stream 115 can be a liquid (or homogeneous) ora supported (or heterogeneous) catalyst system containing the first andsecond transition metal compounds. A sample stream 134 from the catalystsystem feed stream 115 can be submitted to the analytical system 140 fordetermination of the respective concentrations of the first and secondtransition metal compounds in the solution portion of the feed stream(e.g., solids or particulates in the catalyst system feed stream 115 canbe removed prior to analysis).

The polymerization reactor system 100 includes a sample stream 136 fromthe reactor 120. The sample stream 136 from the reactor 120 can besubmitted to the analytical system 140 for determination of therespective concentrations of the first and second transition metalcompounds in the solution portion of the reactor contents (e.g., solidsor particulates in the reactor sample stream 136 can be removed prior toanalysis).

Information or data 145 on the concentrations of the first and secondtransition metal compounds from the analytical system 140 can beprovided to controller 150, which can then control or adjust 155 a flowrate of the combined feed stream 105, and/or a flow rate of the catalystsystem feed stream 115. Alternatively, or additionally, controller 150can independently control or adjust 155 a flow rate of the firsttransition metal compound solution feed stream 102 and/or the secondtransition metal compound solution feed stream 104 to control or adjust155 a relative flow rate of feed streams 102 and 104. Thus, thecontroller 150 controls or adjusts 155 the flow rates of the first andsecond transition metal compounds into the reactor 120 based on, oraccording to, the concentrations determined by the analytical system140. For example, if the concentration determined by the analyticalsystem 140 is too low, the flow rate of one or more feed streams can beincreased by the controller 150.

The disclosed polymerization reactor systems and methods of operatingsame are intended to encompass any olefin polymerization process usingany/all types of polymerization reactors and polymerization reactionconditions. As used herein, “polymerization reactor” includes anypolymerization reactor capable of polymerizing (inclusive ofoligomerizing) olefin monomers and comonomers (one or more than onecomonomer, if used) to produce homopolymers, copolymers, terpolymers,and the like. The various types of polymerization reactors include thosethat can be referred to as a slurry reactor, gas-phase reactor, solutionreactor, high pressure reactor, tubular reactor, autoclave reactor, andthe like, including combinations thereof. The polymerization conditionsfor the various reactor types are well known to those of skill in theart. Gas phase reactors can comprise fluidized bed reactors or stagedhorizontal reactors. Slurry reactors can comprise vertical or horizontalloops. High pressure reactors can comprise autoclave or tubularreactors. These reactor types generally can be operated continuously.Continuous processes can use intermittent or continuous polymer productdischarge. Polymerization reactor systems and processes also can includepartial or full direct recycle of unreacted monomer, unreactedcomonomer, and/or diluent.

Polymerization reactor systems disclosed herein can comprise one type ofpolymerization reactor or multiple reactors of the same or differenttype. For instance, the polymerization reactor system can comprise asolution reactor, a gas-phase reactor, a slurry reactor, or acombination of two or more of these reactors. Production of polymers inmultiple reactors can include several stages in at least two separatepolymerization reactors interconnected by a transfer device making itpossible to transfer the polymer resulting from the first polymerizationreactor into the second reactor. The polymerization conditions in one ofthe reactors can be different from the operating conditions of the otherreactor(s). Alternatively, polymerization in multiple reactors caninclude the manual transfer of polymer from one reactor to subsequentreactors for continued polymerization. Multiple reactor systems caninclude any combination including, but not limited to, multiple loopreactors, multiple gas phase reactors, a combination of loop and gasphase reactors, multiple high pressure reactors, or a combination ofhigh pressure with loop and/or gas phase reactors. The multiple reactorscan be operated in series, in parallel, or both.

According to one aspect, the polymerization reactor system can compriseat least one loop slurry reactor, e.g., comprising vertical orhorizontal loops. Monomer, diluent, catalyst, and optional comonomer canbe continuously fed to a loop reactor where polymerization occurs.Generally, continuous processes can comprise the continuous introductionof monomer/comonomer, a catalyst, and a diluent into a polymerizationreactor and the continuous removal from this reactor of a suspensioncomprising polymer particles and the diluent. Reactor effluent can beflashed to remove the solid polymer from the liquids that comprise thediluent, monomer and/or comonomer. Various technologies can be used forthis separation step including, but not limited to, flashing that caninclude any combination of heat addition and pressure reduction,separation by cyclonic action in either a cyclone or hydrocyclone, orseparation by centrifugation.

A typical slurry polymerization process (also known as the particle formprocess) is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191, 6,833,415, and8,822,608, each of which is incorporated herein by reference in itsentirety.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used, such as can be employed in the bulkpolymerization of propylene to form polypropylene homopolymers.

According to yet another aspect, the polymerization reactor system cancomprise at least one gas phase reactor (e.g., a fluidized bed reactor).Such reactor systems can employ a continuous recycle stream containingone or more monomers continuously cycled through a fluidized bed in thepresence of the catalyst under polymerization conditions. A recyclestream can be withdrawn from the fluidized bed and recycled back intothe reactor. Simultaneously, polymer product can be withdrawn from thereactor and new or fresh monomer can be added to replace the polymerizedmonomer. Such gas phase reactors can comprise a process for multi-stepgas-phase polymerization of olefins, in which olefins are polymerized inthe gaseous phase in at least two independent gas-phase polymerizationzones while feeding a catalyst-containing polymer formed in a firstpolymerization zone to a second polymerization zone. One type of gasphase reactor is disclosed in U.S. Pat. Nos. 5,352,749, 4,588,790,5,436,304, 7,531,606, and 7,598,327, each of which is incorporated byreference in its entirety herein.

According to still another aspect, the polymerization reactor system cancomprise a high pressure polymerization reactor, e.g., can comprise atubular reactor or an autoclave reactor. Tubular reactors can haveseveral zones where fresh monomer, initiators, or catalysts are added.Monomer can be entrained in an inert gaseous stream and introduced atone zone of the reactor. Initiators, catalysts, and/or catalystcomponents can be entrained in a gaseous stream and introduced atanother zone of the reactor. The gas streams can be intermixed forpolymerization. Heat and pressure can be employed appropriately in suchhigh pressure polymerization reactors to obtain optimal polymerizationreaction conditions.

According to yet another aspect, the polymerization reactor system cancomprise a solution polymerization reactor, wherein themonomer/comonomer can be contacted with the catalyst composition bysuitable stirring or other means. A carrier comprising an inert organicdiluent or excess monomer can be employed. If desired, themonomer/comonomer can be brought in the vapor phase into contact withthe catalytic reaction product, in the presence or absence of liquidmaterial. The polymerization zone can be maintained at temperatures(e.g., up to between 150° C. and 180° C.) and pressures that will resultin the formation of a solution of the polymer in a reaction medium.Agitation can be employed to obtain better temperature control and tomaintain uniform polymerization mixtures throughout the polymerizationzone. Adequate means are utilized for dissipating the exothermic heat ofpolymerization.

In some aspects, the polymerization reactor system can comprise anycombination of a raw material feed system, a feed system for catalystand/or catalyst components, and/or a polymer recovery system, includingcontinuous systems. In other aspects, suitable reactor systems cancomprise systems for feedstock purification, catalyst storage andpreparation, extrusion, reactor cooling, polymer recovery,fractionation, recycle, storage, loadout, laboratory analysis, andprocess control.

Polymerization conditions that can be monitored, adjusted, and/orcontrolled for efficiency and to provide desired polymer properties caninclude, but are not limited to, reactor temperature, reactor pressure,catalyst system flow rate into the reactor, monomer flow rate (andcomonomer, if employed) into the reactor, monomer concentration in thereactor, olefin polymer output rate, recycle rate, hydrogen flow rate(if employed), reactor cooling status, and the like. Polymerizationtemperature can affect catalyst productivity, polymer molecular weight,and molecular weight distribution. A suitable polymerization temperaturecan be any temperature below the de-polymerization temperature accordingto the Gibbs Free energy equation. Typically, this includes from about60° C. to about 280° C., for example, from about 60° C. to about 185°C., from about 60° C. to about 115° C., or from about 130° C. to about180° C., depending upon the type of polymerization reactor, the polymergrade, and so forth. In some reactor systems, the polymerization reactortemperature generally can be within a range from about 70° C. to about110° C., or from about 125° C. to about 175° C.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor typically can be less than 1000 psig (6.9 MPa). Thepressure for gas phase polymerization usually can be in the 200 psig to500 psig range (1.4 MPa to 3.4 MPa). High pressure polymerization intubular or autoclave reactors generally can be conducted at about 20,000psig to 75,000 psig (138 MPa to 517 MPa). Polymerization reactors canalso be operated in a supercritical region occurring at generally highertemperatures and pressures (for instance, above 92° C. and 700 psig(4.83 MPa)). Operation above the critical point of apressure/temperature diagram (supercritical phase) can offer advantagesto the polymerization reaction process.

The concentration of the reactants entering the polymerization reactorcan be controlled to produce resins with certain physical and mechanicalproperties. The proposed end-use product that will be formed by thepolymer resin and the method of forming that product ultimately candetermine the desired polymer properties and attributes. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxation,and hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization,stereoregularity, crack growth, long chain branching, and rheologicalmeasurements.

Aspects contemplated herein also are directed to, and encompass, thepolymers (or oligomers) produced by any of the polymerization reactorsystems and methods disclosed herein. Articles of manufacture can beformed from, and/or can comprise, the polymers (or oligomers) producedin accordance with the systems and methods described herein.

Catalyst Systems

The methods, processes, and reactor systems disclosed herein areapplicable to any catalyst system suitable for the polymerization of anolefin monomer, but are not limited thereto. Herein, a “catalyst system”also can be referred to as a “catalyst composition” or a “catalystmixture.” The first and second transition metal compounds independentlycan comprise, for example, a transition metal (one or more than one)from Groups 3-12 of the Periodic Table of the Elements (Chemical andEngineering News, 63(5), 27, 1985). In one aspect, the first and/orsecond transition metal compound can comprise a Group 3, 4, 5, or 6transition metal, or a combination of two or more transition metals. Thefirst and/or second transition metal compound(s) independently cancomprise chromium, vanadium, titanium, zirconium, hafnium, or acombination thereof, in some aspects, or can comprise chromium,titanium, zirconium, hafnium, or a combination thereof, in otheraspects. Accordingly, the first and/or second transition metalcompound(s) independently can comprise chromium, or titanium, orzirconium, or hafnium, either singly or in combination. Moreover,catalyst systems containing more than two transition metal compounds arecontemplated herein, and these additional transition metal compounds(e.g., a third transition metal compound) independently can comprise anysuitable transition metal, such as chromium, titanium, zirconium,hafnium, vanadium, or a combination thereof.

In certain aspects of this invention, the first and/or second transitionmetal compound(s), independently, can comprise any suitablenon-metallocene compound. Generally, the methods, processes, and reactorsystems disclosed herein are most applicable to transition metalcompounds, such as non-metallocene compounds, where the absorbancecharacteristics of the first transition metal compound and the secondtransition metal compound overlap, and cannot be de-convoluted.

Illustrative and non-limiting examples of suitable transition metalcompounds encompassed herein can include the following compounds (R andR′=halide or C₁-C₁₈ hydrocarbyl group, n=an integer from 0 to 4,Ph=phenyl, tBu=tert-butyl, py=pyridine):

Alternatively or additionally, in certain aspects, the first and/orsecond transition metal compound(s) independently can comprise ametallocene compound, and the metallocene compound can comprise anunbridged metallocene compound. In one aspect, the metallocene compoundcan comprise an unbridged zirconium or hafnium based metallocenecompound and/or an unbridged zirconium and/or hafnium based dinuclearmetallocene compound. In another aspect, the metallocene compound cancomprise an unbridged zirconium or hafnium based metallocene compoundcontaining two indenyl groups or a cyclopentadienyl and an indenylgroup. In yet another aspect, the metallocene compound can comprise anunbridged zirconium or hafnium based metallocene compound containing twoindenyl groups. In still another aspect, the metallocene compound cancomprise an unbridged zirconium or hafnium based metallocene compoundcontaining a cyclopentadienyl and an indenyl group.

In an aspect, the metallocene compound can comprise an unbridgedzirconium based metallocene compound containing two indenyl groups or acyclopentadienyl and an indenyl group, while in another aspect, themetallocene compound can comprise a dinuclear unbridged metallocenecompound with an alkenyl linking group.

Illustrative and non-limiting examples of unbridged metallocenecompounds that are suitable for use as transition metal compoundsdescribed herein can include the following compounds (Ph=phenyl,stereochemistry not shown):

and the like, as well as combinations thereof.

The first and/or second transition metal compound(s) is/are not limitedsolely to unbridged metallocene compounds such as described above, or tosuitable unbridged metallocene compounds disclosed in U.S. Pat. Nos.7,199,073, 7,226,886, 7,312,283, and 7,619,047, which are incorporatedherein by reference in their entirety. For example, the first and/orsecond transition metal compound(s) can comprise an unbridged dinuclearmetallocene compound, such as those described in U.S. Pat. Nos.7,919,639 and 8,080,681, the disclosures of which are incorporatedherein by reference in their entirety. Illustrative and non-limitingexamples of dinuclear metallocene compounds suitable for use in thepresent invention can include the following compounds (stereochemistrynot shown):

and the like, as well as combinations thereof.

Additionally or alternatively, the first and/or second transition metalcompound(s) independently can comprise a bridged metallocene compound.In one aspect, the bridged metallocene compound can comprise a bridgedzirconium or hafnium based metallocene compound. In another aspect, thebridged metallocene compound can comprise a bridged zirconium or hafniumbased metallocene compound with an alkenyl substituent. In yet anotheraspect, the bridged metallocene compound can comprise a bridgedzirconium or hafnium based metallocene compound with an alkenylsubstituent and a fluorenyl group. In still another aspect, the bridgedmetallocene compound can comprise a bridged zirconium or hafnium basedmetallocene compound with a cyclopentadienyl group and a fluorenylgroup, and with an alkenyl substituent on the bridging group and/or onthe cyclopentadienyl group.

In an aspect, the bridged metallocene compound can comprise a singleatom bridged metallocene compound with a fluorenyl group. In anotheraspect, the bridged metallocene compound can comprise a single atombridged metallocene compound with a fluorenyl group and either acyclopentadienyl group or an indenyl group. In yet another aspect, thebridged metallocene compound can comprise a single atom bridgedmetallocene compound with a fluorenyl group and a cyclopentadienylgroup. In still another aspect, the bridged metallocene compound cancomprise a single atom bridged metallocene compound with a fluorenylgroup and an indenyl group.

In these and other aspects, the bridged metallocene compound can containan aryl substituent (e.g., a phenyl group) on the bridging atom.Additionally or alternatively, the bridged metallocene compound cancontain an alkenyl substituent, for example, on the bridging atom,and/or on the fluorenyl group, and/or on the cyclopentadienyl or indenylgroup.

Illustrative and non-limiting examples of suitable bridged metallocenecompounds encompassed herein can include the following compounds(Me=methyl, Ph=phenyl, t-Bu=tert-butyl, stereochemistry not shown):

and the like, as well as combinations thereof.

Further examples of bridged metallocene compounds that are suitable foruse as described herein can include, but are not limited to, thefollowing compounds (stereochemistry not shown):

and the like, as well as combinations thereof.

The first and/or second transition metal compound(s) is/are not limitedsolely to the bridged metallocene compounds such as described above.Other suitable bridged metallocene compounds are disclosed in U.S. Pat.Nos. 7,026,494, 7,041,617, 7,226,886, 7,312,283, 7,517,939, 7,619,047,8,288,487, 8,329,834, 8,629,292, and 9,040,642, all of which areincorporated herein by reference in their entirety.

The catalyst system, in addition to the first transition metal compoundand the second transition metal compound, can comprise an activator (oneor more) and an optional co-catalyst. Illustrative activators caninclude, but are not limited to, aluminoxane compounds, organoboron ororganoborate compounds, ionizing ionic compounds, activator-supports(e.g., a solid oxide treated with an electron-withdrawing anion), andthe like, or combinations thereof. Commonly used polymerizationco-catalysts can include, but are not limited to, metal alkyl, ororganometal, co-catalysts, with the metal encompassing boron, aluminum,and the like. For instance, alkyl boron and/or organoaluminum (e.g.,alkyl aluminum) compounds often can be used as co-catalysts in acatalyst system. Representative compounds can include, but are notlimited to, tri-n-butyl borane, tripropylborane, triethylborane,trimethylaluminum, triethylaluminum, tri-n-propylaluminum,tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum,tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminumethoxide, diethylaluminum chloride, and the like, including combinationsthereof.

Co-catalysts that can be used in the catalyst systems of this inventionare not limited to the co-catalysts described above. Other suitableco-catalysts are well known to those of skill in the art including, forexample, those disclosed in U.S. Pat. Nos. 3,242,099, 4,794,096,4,808,561, 5,576,259, 5,807,938, 5,919,983, 7,294,599 7,601,665,7,884,163, 8,114,946, and 8,309,485, which are incorporated herein byreference in their entirety.

Solid Oxides

In some aspects, the catalyst system can contain a solid oxide.Generally, the solid oxide can comprise oxygen and one or more elementsselected from Group 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 ofthe periodic table, or comprise oxygen and one or more elements selectedfrom the lanthanide or actinide elements (See: Hawley's CondensedChemical Dictionary, 11^(th) Ed., John Wiley & Sons, 1995; Cotton, F.A., Wilkinson, G., Murillo, C. A., and Bochmann, M., Advanced InorganicChemistry, 6^(th) Ed., Wiley-Interscience, 1999). For example, the solidinorganic oxide can comprise oxygen and an element, or elements,selected from Al, B, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, La, Mn, Mo, Ni, Sb,Si, Sn, Sr, Th, Ti, V, W, P, Y, Zn, and Zr.

Suitable examples of solid oxide materials or compounds that can be usedas components of a catalyst system can include, but are not limited to,Al₂O₃, B₂O₃, BeO, Bi₂O₃, CdO, Co₃O₄, Cr₂O₃, CuO, Fe₂O₃, Ga₂O₃, La₂O₃,Mn₂O₃, MoO₃, NiO, P₂O₅, Sb₂O₅, SiO₂, SnO₂, SrO, ThO₂, TiO₂, V₂O₅, WO₃,Y₂O₃, ZnO, ZrO₂, and the like, including mixed oxides thereof, andcombinations thereof.

The solid oxide can encompass oxide materials such as alumina, “mixedoxide” compounds thereof such as silica-alumina, and combinations ormixtures of more than one solid oxide material. Mixed oxides such assilica-alumina can be single or multiple chemical phases with more thanone metal combined with oxygen to form the solid oxide. Examples ofmixed oxides that can be used herein include, but are not limited to,silica-alumina, silica-coated alumina, silica-titania, silica-zirconia,alumina-titania, alumina-zirconia, zinc-aluminate, alumina-boria,silica-boria, aluminum phosphate, aluminophosphate,aluminophosphate-silica, titania-zirconia, and the like, or acombination thereof. Silica-coated aluminas are encompassed herein; suchoxide materials are described in, for example, U.S. Pat. No. 7,884,163,the disclosure of which is incorporated herein by reference in itsentirety.

The percentage of each oxide in a mixed oxide can vary depending uponthe respective oxide materials. As an example, a silica-aluminatypically has an alumina content from 5% by weight to 95% by weight.According to one aspect, the alumina content of the silica-alumina canbe from 5% alumina by weight to 50% alumina by weight, or from 8% to 30%alumina by weight. In another aspect, high alumina contentsilica-alumina compounds can be employed, in which the alumina contentof these silica-alumina materials typically ranges from 60% alumina byweight to 90% alumina by weight, or from 65% alumina by weight to 80%alumina by weight.

In one aspect, the solid oxide can comprise silica-alumina,silica-coated alumina, silica-titania, silica-zirconia, alumina-titania,alumina-zirconia, zinc-aluminate, alumina-boria, silica-boria, aluminumphosphate, aluminophosphate, aluminophosphate-silica, titania-zirconia,or a combination thereof; alternatively, silica-alumina; alternatively,silica-coated alumina; alternatively, silica-titania; alternatively,silica-zirconia; alternatively, alumina-titania; alternatively,alumina-zirconia; alternatively, zinc-aluminate; alternatively,alumina-boria; alternatively, silica-boria; alternatively, aluminumphosphate; alternatively, aluminophosphate; alternatively,aluminophosphate-silica; or alternatively, titania-zirconia.

In another aspect, the solid oxide can comprise silica, alumina,titania, zirconia, magnesia, boria, zinc oxide, a mixed oxide thereof,or any mixture thereof. For instance, the solid oxide can comprisesilica, alumina, titania, or a combination thereof; alternatively,silica; alternatively, alumina; alternatively, titania; alternatively,zirconia; alternatively, magnesia; alternatively, boria; oralternatively, zinc oxide.

In some aspects, the solid oxide can have a pore volume greater than 0.1cc/g, or alternatively, greater than 0.5 cc/g. Often, the solid oxidecan have a pore volume greater than 1.0 cc/g. Additionally, oralternatively, the solid oxide can have a surface area greater than 100m²/g; alternatively, greater than 250 m²/g; or alternatively, greaterthan 350 m²/g. For example, the solid oxide can have a surface area offrom 100 to 1000 m²/g, from 200 to 800 m²/g, or from 250 to 600 m²/g.

Activator-Supports

The present invention encompasses various catalyst systems which cancontain an activator-support. In one aspect, the activator-support cancomprise a solid oxide treated with an electron-withdrawing anion.Alternatively, in another aspect, the activator-support can comprise asolid oxide treated with an electron-withdrawing anion, the solid oxidecontaining a Lewis-acidic metal ion. Non-limiting examples of suitableactivator-supports are disclosed in, for instance, U.S. Pat. Nos.7,294,599, 7,601,665, 7,884,163, 8,309,485, 8,623,973, and 8,703,886,which are incorporated herein by reference in their entirety.

The solid oxide can encompass oxide materials such as alumina, “mixedoxides” thereof such as silica-alumina, coatings of one oxide onanother, and combinations and mixtures thereof. The mixed oxides such assilica-alumina can be single or multiple chemical phases with more thanone metal combined with oxygen to form the solid oxide. Examples ofmixed oxides that can be used to form an activator-support, eithersingly or in combination, can include, but are not limited to,silica-alumina, silica-titania, silica-zirconia, alumina-titania,alumina-zirconia, zinc-aluminate, alumina-boria, silica-boria,aluminophosphate-silica, titania-zirconia, and the like. The solid oxideused herein also can encompass oxide materials such as silica-coatedalumina, as described in U.S. Pat. No. 7,884,163.

Accordingly, in one aspect, the solid oxide can comprise silica,alumina, silica-alumina, silica-coated alumina, aluminum phosphate,aluminophosphate, heteropolytungstate, titania, silica-titania,zirconia, silica-zirconia, magnesia, boria, zinc oxide, any mixed oxidethereof, or any combination thereof. In another aspect, the solid oxidecan comprise alumina, silica-alumina, silica-coated alumina, aluminumphosphate, aluminophosphate, heteropolytungstate, titania,silica-titania, zirconia, silica-zirconia, magnesia, boria, or zincoxide, as well as any mixed oxide thereof, or any mixture thereof. Inanother aspect, the solid oxide can comprise silica, alumina, titania,zirconia, magnesia, boria, zinc oxide, any mixed oxide thereof, or anycombination thereof. In yet another aspect, the solid oxide can comprisesilica-alumina, silica-coated alumina, silica-titania, silica-zirconia,alumina-boria, or any combination thereof. In still another aspect, thesolid oxide can comprise alumina, silica-alumina, silica-coated alumina,or any mixture thereof alternatively, alumina; alternatively,silica-alumina; or alternatively, silica-coated alumina.

The silica-alumina or silica-coated alumina solid oxide materials whichcan be used can have a silica content from about 5% by weight to about95% by weight. In one aspect, the silica content of these solid oxidescan be from about 10% by weight to about 80% silica by weight, or fromabout 20% by weight to about 70% silica by weight. In another aspect,such materials can have silica contents ranging from about 15% to about60% silica by weight, or from about 25% to about 50% silica by weight.The solid oxides contemplated herein can have any suitable surface area,pore volume, and particle size, as would be recognized by those of skillin the art.

The electron-withdrawing component used to treat the solid oxide can beany component that increases the Lewis or Brønsted acidity of the solidoxide upon treatment (as compared to the solid oxide that is not treatedwith at least one electron-withdrawing anion). According to one aspect,the electron-withdrawing component can be an electron-withdrawing anionderived from a salt, an acid, or other compound, such as a volatileorganic compound, that serves as a source or precursor for that anion.Examples of electron-withdrawing anions can include, but are not limitedto, sulfate, bisulfate, fluoride, chloride, bromide, iodide,fluorosulfate, fluoroborate, phosphate, fluorophosphate,trifluoroacetate, triflate, fluorozirconate, fluorotitanate,phospho-tungstate, tungstate, molybdate, and the like, includingmixtures and combinations thereof. In addition, other ionic or non-ioniccompounds that serve as sources for these electron-withdrawing anionsalso can be employed. It is contemplated that the electron-withdrawinganion can be, or can comprise, fluoride, chloride, bromide, phosphate,triflate, bisulfate, or sulfate, and the like, or any combinationthereof, in some aspects provided herein. In other aspects, theelectron-withdrawing anion can comprise sulfate, bisulfate, fluoride,chloride, bromide, iodide, fluorosulfate, fluoroborate, phosphate,fluorophosphate, trifluoroacetate, triflate, fluorozirconate,fluorotitanate, and the like, or combinations thereof. Yet, in otheraspects, the electron-withdrawing anion can comprise fluoride and/orsulfate.

The activator-support generally can contain from about 1 wt. % to about25 wt. % of the electron-withdrawing anion, based on the weight of theactivator-support. In particular aspects provided herein, theactivator-support can contain from about 1 to about 20 wt. %, from about2 wt. % to about 20 wt. %, from about 3 wt. % to about 20 wt. %, fromabout 2 wt. % to about 15 wt. %, from about 3 wt. % to about 15 wt. %,from about 3 wt. % to about 12 wt. %, or from about 4 wt. % to about 10wt. %, of the electron-withdrawing anion, based on the total weight ofthe activator-support.

In an aspect, the activator-support can comprise fluorided alumina,chlorided alumina, bromided alumina, sulfated alumina, fluoridedsilica-alumina, chlorided silica-alumina, bromided silica-alumina,sulfated silica-alumina, fluorided silica-zirconia, chloridedsilica-zirconia, bromided silica-zirconia, sulfated silica-zirconia,fluorided silica-titania, fluorided silica-coated alumina,fluorided-chlorided silica-coated alumina, sulfated silica-coatedalumina, phosphated silica-coated alumina, and the like, as well as anymixture or combination thereof. In another aspect, the activator-supportemployed in the catalyst systems described herein can be, or cancomprise, a fluorided solid oxide and/or a sulfated solid oxide,non-limiting examples of which can include fluorided alumina, sulfatedalumina, fluorided silica-alumina, sulfated silica-alumina, fluoridedsilica-zirconia, fluorided silica-coated alumina, sulfated silica-coatedalumina, and the like, as well as combinations thereof. In yet anotheraspect, the activator-support can comprise fluorided alumina;alternatively, chlorided alumina; alternatively, sulfated alumina;alternatively, fluorided silica-alumina; alternatively, sulfatedsilica-alumina; alternatively, fluorided silica-zirconia; alternatively,chlorided silica-zirconia; alternatively, sulfated silica-coatedalumina; alternatively, fluorided-chlorided silica-coated alumina; oralternatively, fluorided silica-coated alumina. In some aspects, theactivator-support can comprise a fluorided solid oxide, while in otheraspects, the activator-support can comprise a sulfated solid oxide.

Various processes can be used to form activator-supports useful in thepresent invention. Methods of contacting the solid oxide with theelectron-withdrawing component, suitable electron withdrawing componentsand addition amounts, impregnation with metals or metal ions (e.g.,zinc, nickel, vanadium, titanium, silver, copper, gallium, tin,tungsten, molybdenum, zirconium, and the like, or combinations thereof),and various calcining procedures and conditions are disclosed in, forexample, U.S. Pat. Nos. 6,107,230, 6,165,929, 6,294,494, 6,300,271,6,316,553, 6,355,594, 6,376,415, 6,388,017, 6,391,816, 6,395,666,6,524,987, 6,548,441, 6,548,442, 6,576,583, 6,613,712, 6,632,894,6,667,274, 6,750,302, 7,294,599, 7,601,665, 7,884,163, and 8,309,485,which are incorporated herein by reference in their entirety. Othersuitable processes and procedures for preparing activator-supports(e.g., fluorided solid oxides and sulfated solid oxides) are well knownto those of skill in the art.

Olefin Monomers and Olefin Polymers

Olefin monomers contemplated herein typically include olefin compoundshaving from 2 to 30 carbon atoms per molecule and having at least oneolefinic double bond. Homopolymerization processes using a singleolefin, such as ethylene, propylene, butene, hexene, octene, and thelike, are encompassed, as well as copolymerization, homopolymerization,terpolymerization, and similar polymerization reactions using an olefinmonomer with at least one different olefinic compound. As previouslydisclosed, polymerization processes are meant to encompassoligomerization processes as well.

As an example, any resultant ethylene copolymers or terpolymersgenerally can contain a major amount of ethylene (>50 mole percent) anda minor amount of comonomer (<50 mole percent). Comonomers that can becopolymerized with ethylene often have from 3 to 20 carbon atoms intheir molecular chain.

Acyclic, cyclic, polycyclic, terminal (a), internal, linear, branched,substituted, unsubstituted, functionalized, and non-functionalizedolefins can be employed. For example, typical unsaturated compounds thatcan be polymerized to produce olefin polymers can include, but are notlimited to, ethylene, propylene, 1-butene, 2-butene, 3-methyl-1-butene,isobutylene, 1-pentene, 2-pentene, 3-methyl-1-pentene,4-methyl-1-pentene, 1-hexene, 2-hexene, 3-hexene, 3-ethyl-1-hexene,1-heptene, 2-heptene, 3-heptene, the four normal octenes (e.g.,1-octene), the four normal nonenes, the five normal decenes, and thelike, or mixtures of two or more of these compounds. Cyclic and bicyclicolefins, including but not limited to, cyclopentene, cyclohexene,norbornylene, norbornadiene, and the like, also can be polymerized asdescribed herein. Styrene also can be employed as a monomer or as acomonomer. In an aspect, the olefin monomer can comprise a C₂-C₂₄olefin; alternatively, a C₂-C₁₂ olefin; alternatively, a C₆-C₂₄ olefin;alternatively, a C₂-C₁₀ α-olefin; alternatively, propylene, 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, or styrene;alternatively, ethylene, propylene, 1-butene, 1-hexene, or 1-octene;alternatively, ethylene or propylene; alternatively, ethylene; oralternatively, propylene.

When a copolymer (or alternatively, a terpolymer) is desired, the olefinmonomer can comprise, for example, ethylene or propylene, which iscopolymerized with at least one comonomer. According to one aspect, theolefin monomer in the polymerization process can comprise ethylene. Inthis aspect, examples of suitable olefin comonomers can include, but arenot limited to, propylene, 1-butene, 2-butene, 3-methyl-1-butene,isobutylene, 1-pentene, 2-pentene, 3-methyl-1-pentene,4-methyl-1-pentene, 1-hexene, 2-hexene, 3-ethyl-1-hexene, 1-heptene,2-heptene, 3-heptene, 1-octene, 1-decene, styrene, and the like, orcombinations thereof. According to another aspect, the olefin monomercan comprise ethylene and the olefin comonomer can comprise an α-olefin,while in yet another aspect, the comonomer can comprise propylene,1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, styrene, or anycombination thereof; or alternatively, the olefin comonomer can comprise1-butene, 1-hexene, 1-octene, or a combination thereof.

Generally, the amount of comonomer introduced into a polymerizationreactor to produce the copolymer can be from about 0.01 weight percent(wt. %) to about 50 weight percent of the comonomer based on the totalweight of the monomer and comonomer. According to another aspect, theamount of comonomer introduced into a polymerization reactor can be fromabout 0.01 weight percent to about 40 weight percent comonomer based onthe total weight of the monomer and comonomer. In still another aspect,the amount of comonomer introduced into a polymerization reactor can befrom about 0.1 weight percent to about 35 weight percent comonomer basedon the total weight of the monomer and comonomer. Yet, in anotheraspect, the amount of comonomer introduced into a polymerization reactorcan be from about 0.5 weight percent to about 20 weight percentcomonomer based on the total weight of the monomer and comonomer.

According to one aspect, at least one monomer/reactant can be ethylene,so the polymerization reaction can be a homopolymerization involvingonly ethylene, or a copolymerization with a different acyclic, cyclic,terminal, internal, linear, branched, substituted, or unsubstitutedolefin. In addition, the methods disclosed herein intend for olefin toalso encompass diolefin compounds that include, but are not limited to,1,3-butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, and the like.

Olefin polymers encompassed herein can include any polymer (or oligomer)produced from any olefin monomer (and optional comonomer(s)) describedherein. For example, the olefin polymer can comprise an ethylenehomopolymer, a propylene homopolymer, an ethylene copolymer (e.g.,ethylene/1-butene, ethylene/1-hexene, or ethylene/l-octene), a propylenerandom copolymer, a propylene block copolymer, and the like, includingcombinations thereof. Moreover, the olefin polymer (or oligomer) cancomprise, in certain aspects, an olefin dimer, olefin trimer, or olefintetramer, and including mixtures or combinations thereof. Thus, olefinpolymer encompasses oligomerization products of C₆-C₂₄ olefins (orC₆-C₂₄ α-olefins, or 1-hexene, or 1-octene, or 1-decene, or 1-dodecene,or 1-tetradecene, or 1-hexadecene).

Expanding to Three or More Transition Metal Compounds Disclosed hereinare methods for determining the respective concentrations of twodifferent transition metal compounds in a solution comprising the twodifferent transition metal compounds, as well as related polymerizationreactor systems and processes for operating polymerization reactorsystems. However, the methods, processes, and systems are not limited tosolutions containing only two transition metal compounds. The methods,processes, and systems disclosed herein also are applicable to solutionscontaining three or more different transition metal compounds, e.g.,three different transition metal compounds, four different transitionmetal compounds, and so forth. As one of skill in the art would readilyrecognize, when three or more transition metal compounds are present inthe solution—for example, from three to five different compounds—theaccuracy of determining the respective concentration of each transitionmetal compound in the solution can depend greatly on the degree ofoverlap of the respective absorbance profiles (for each transition metalcompound) at key absorbance wavelengths. For instance, in a solutioncontaining compound 1 having a peak absorbance at 350 nm, compound 2having a peak absorbance at 425 nm, compound 3 having a peak absorbanceat 500 nm, and compound 4 having a peak absorbance at 575 nm, it may beeasy to determine the respective concentrations of each compound withhigh accuracy.

Encompassed herein is a method for determining a first concentration ofa first transition metal compound, a second concentration of a secondtransition metal compound, and a third concentration of a thirdtransition metal compound, in a solution comprising the first transitionmetal compound, the second transition metal compound, and the thirdtransition metal compound. This method can comprise (or consistessentially of, or consist of) (i) providing a first referenceabsorbance profile (F₁) of the first transition metal compound in afirst reference solution at a first known concentration, a secondreference absorbance profile (F₂) of the second transition metalcompound in a second reference solution at a second known concentration,and a third reference absorbance profile (F₃) of the third transitionmetal compound in a third reference solution at a third knownconcentration, (ii) submitting a sample of the solution to a samplechamber, (iii) irradiating the sample in the chamber with a light beamat a wavelength (e.g., a range of wavelengths) in the UV-visiblespectrum, (iv) generating (e.g., collecting or outputting) a sampleabsorbance profile of the sample, and calculating a curve having theformula β₁F₁+β₂F₂+β₃F₃ to fit the sample absorbance profile to aleast-squares regression fit value (R²) of at least 0.9 (and often atleast 0.99, or more), wherein β₁ is a first weighting coefficient, F₁ isthe first reference absorbance profile of the first transition metalcompound in the first reference solution at the first knownconcentration, β₂ is a second weighting coefficient, F₂ is the secondreference absorbance profile of the second transition metal compound inthe second reference solution at the second known concentration, β₃ is athird weighting coefficient, and F₃ is the third reference absorbanceprofile of the third transition metal compound in the third referencesolution at the third known concentration, and (v) multiplying the firstknown concentration with β₁ to determine the first concentration of thefirst transition metal compound in the solution, multiplying the secondknown concentration with β₂ to determine the second concentration of thesecond transition metal compound in the solution, and multiplying thethird known concentration with β₃ to determine the third concentrationof the third transition metal compound in the solution.

In like manner, the method can be expanded to determine the respectiveconcentrations of four different transition metal compounds, or fivedifferent transition metal compounds, etc., in a solution containing thefour transition metal compounds, five transition metal compounds, etc.

Any of the features and aspects disclosed herein for analytical methods,polymerization reactor systems, and processes for operatingpolymerization reactor systems that pertain to solutions containing twotransition metal compounds are equally applicable to solutionscontaining three or more transition metal compounds, and these featuresand aspects can be used without limitation and in any combination todescribe analytical methods, polymerization reactor systems, andprocesses for operating polymerization reactor systems relating tosolutions containing three or more transition metal compounds.

EXAMPLES

The invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, modifications, and equivalentsthereof which, after reading the description herein, can suggestthemselves to one of ordinary skill in the art without departing fromthe spirit of the present invention or the scope of the appended claims.

The chemical structures for the first, second, and third transitionmetal compounds used in the examples are provided below as MET-1, MET-2,and MET-3, respectively.

Solutions Containing One Transition Metal Compound

Separate stock solutions of MET-1 and MET-2 were prepared and used tofurther prepare the transition metal compound solutions of varyingconcentrations used in the examples. To prepare the stock solutions, therespective transition metal compound was weighed into a metal weigh panusing an analytical balance contained in a glovebox. The gloveboxatmosphere was maintained at less than 0.1 ppm oxygen and less than 0.1ppm water. The solvent (either 1-hexene or toluene) previously driedover molecular sieves was measured to a known volume using a volumetricflask. The entirety of the measured solvent was used to rinse therespective transition metal compound from the metal weigh pan into aglass vial (approximately 20-30 mL in volume) quantitatively. A smallstir bar was added to the vial, and the vial was capped with a septumand metal seal. The contents of the vial were magnetically stirred atabout 1000 rpm in the glovebox and monitored for dissolution.

Dissolution was complete in approximately 30 min, depending on thetransition metal compound, the solvent, and the concentration. In thismanner, four stock solutions were prepared (MET-1 in 1-hexene, MET-1 intoluene, MET-2 in 1-hexene, and MET-2 in toluene). The transition metalcompound concentration in each stock solution was 0.1 wt. %. Then, foreach stock solution, an aliquot of the stock solution was removed bysyringe and added to a separate vial. An equal volume of the samesolvent was added to the aliquot and the vial was loaded with a stir barand capped as before for the stock solution. The mixture was allowed tostir, resulting in a solution possessing half the original concentrationof the stock solution. This procedure was successively repeated toproduce a series of solutions with transition metal concentrationsdecreasing by half each repetition.

The homogeneity of each sample was verified by visual inspection in theglovebox. Quartz cuvettes previously dried in an oven at 110° C. forseveral hours were loaded with their respective lids into the glovebox.One cuvette was loaded with approximately 3-3.5 mL pure solvent (either1-hexene or toluene, and the same solvent used in the respective stocksolutions and dilutions) and capped as a reference cell. The remainingcuvettes were each loaded with approximately 3-3.5 mL of a metallocenesolution and securely capped to prevent accidental exposure to theatmosphere. The cuvettes were removed from the glovebox and analyzedusing a Shimadzu UV-2550 UV-Vis spectrometer. The samples were typicallyanalyzed in the wavelength range of 300-800 nm in 0.5 nm increments.

The raw data from each analysis consisted of a file containing columnardata of wavelength (nm) and absorbance (A.U.). Data from all theanalyzed samples were copied from the raw data files into a singlespreadsheet. Absorbance versus wavelength profiles for the wavelengthrange of 300-600 nm for each combination of (1) transition metalcompound and (2) solvent were plotted in a single chart. Representativecharts are shown in FIG. 2 (MET-2 in toluene), FIG. 4 (MET-2 in1-hexene), FIG. 6 (MET-1 in toluene), and FIG. 8 (MET-1 in 1-hexene).Each transition metal compound in each solvent exhibited acharacteristic peak whose absorbance maximum varied depending onconcentration. Representative wavelengths were selected within thisabsorbance peak (e.g., one at the maximum and two additional, one oneither side of the maximum). For each of the representative wavelengths,absorbance was plotted versus concentration of the transition metalconcentration. Least-squares regression of the absorbance versusconcentration data resulted in a calibration curve for the givencombination of transition metal compound and solvent at thatrepresentative wavelength. Illustrative calibration curves are shown inFIG. 3 (MET-2 in toluene), FIG. 5 (MET-2 in 1-hexene), FIG. 7 (MET-1 intoluene), and FIG. 9 (MET-1 in 1-hexene).

As can be seen from FIGS. 2-9, each UV-Vis absorbance profile dependsupon the transition metal compound, the solvent, and the concentrationof the transition metal compound in the solvent. Additionally, thelinear calibration curves were extremely accurate in correlating themeasured absorbance to the concentration of the respective transitionmetal compound in the solvent at the selected wavelengths: statisticalR² values were greater than 0.99 in all cases.

Solutions Containing Two Transition Metal Compounds

In Example 1, a stock solution of MET-1 in 1-hexene:toluene (9:1, weightbasis) was prepared at a concentration of 0.313 wt. %. Absorbancespectra for MET-1 (1 mm path length) at a concentration of 0.313 wt. %was obtained in the same manner as described above, using only solvent(1-hexene/toluene) in the reference cell. This reference absorbanceprofile for MET-1 is plotted in FIG. 10. Similarly, a stock solution ofMET-2 in 1-hexene:toluene (9:1, weight basis) was prepared at aconcentration of 0.35 wt. %. Absorbance spectra for MET-2 (1 mm pathlength) at a concentration of 0.35 wt. % was obtained in the same manneras described above, using only solvent (1-hexene/toluene) in thereference cell. This reference absorbance profile for MET-2 also isplotted in FIG. 10.

From the respective stock solutions, a control solution containing bothMET-1 and MET-2 at known concentrations was prepared: MET-1 (at 0.026wt. %) and MET-2 (at 0.35 wt. %). Absorbance spectra for this solutionof MET-1 and MET-2 in 1-hexene:toluene (9:1, weight basis) at a 1 mmpath length was obtained in the same manner as described above, usingonly 1-hexene/toluene in the reference cell. This control absorbanceprofile for the solution containing both MET-1 and MET-2 is plotted inFIG. 10.

Using a multiple regression feature in Microsoft Excel, a curve havingthe formula “β₁F₁+β₂F₂” was fit to the control absorbance profile overthe 300-600 nm range. In this formula, β₁ is the weighting coefficientfor MET-1, F₁ is the reference absorbance profile for MET-1 (at 0.313wt. %), β₂ is the weighting coefficient for MET-2, and F₂ is thereference absorbance profile for MET-2 (at 0.35 wt. %). The model curvefor the formula β₁F₁+β₂F₂ is plotted in FIG. 10, where the R² value is0.99997. In FIG. 10, the control absorbance profile curve and themodel/fitted curve completely overlap, and cannot be distinguishedvisually. For the model curve having formula “β₁F₁+β₂F₂” in FIG. 10, β₁is equal 0.092 for MET-1 and β₂ is equal to 1.025 for MET-2. The Sq Resline shows the deviation between the model/fitted curve and theabsorbance profile curve, and by 350 nm, it effectively overlaps thebaseline, indicating the excellent fit of the model/fitted curve.

Multiplying the 0.313 wt. % concentration in the MET-1 reference profilewith β₁ (0.092) results in a predicted concentration of MET-1 in thecontrol solution of approximately 0.029 wt. % (actual is 0.026 wt. %).Likewise, multiplying the 0.35 wt. % concentration in the MET-2reference profile with β₂ (1.025) results in a predicted concentrationof MET-2 in the control solution of approximately 0.359 wt. % (actual is0.35 wt. %). Thus, this method for simultaneously determining theconcentrations of MET-1 and MET-2 results in very accurate predictionsof the respective concentrations.

In Example 2, the same reference absorbance profiles for MET-1 and MET-2as described in Example 1 were used, and these reference profiles areplotted in FIG. 11. A sample solution in which the exact MET-1 and MET-2concentrations were not known was evaluated in Example 2. The only knowninformation on the sample solution was that it contained the samesolvent mixture (1-hexene:toluene at a 9:1 weight ratio) and it had a“target” MET-2 concentration of 0.25 wt. %, although the exactconcentration was not known.

Absorbance spectra for the sample solution of MET-1 and MET-2 in1-hexene:toluene (9:1, weight basis) at a 1 mm path length was obtainedin the same manner as described above, using only 1-hexene/toluene inthe reference cell. The sample absorbance profile for the samplesolution containing both MET-1 and MET-2 is plotted in FIG. 11.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂” wasfit to the sample absorbance profile over the 300-600 nm range. In thisformula, β₁ is the weighting coefficient for MET-1, F₁ is the referenceabsorbance profile for MET-1 (at 0.313 wt. %), β₂ is the weightingcoefficient for MET-2, and F₂ is the reference absorbance profile forMET-2 (at 0.35 wt. %). The model curve for the formula β₁F₁+β₂F₂ isplotted in FIG. 11, where the R² value is 0.99991. In FIG. 11, thesample absorbance profile curve and the model/fitted curve completelyoverlap, and cannot be distinguished visually. For the model curvehaving formula “β₁F₁+β₂F₂” in FIG. 11, β₁ is equal 0.131 for MET-1 andβ₂ is equal to 0.752 for MET-2.

Multiplying the 0.313 wt. % concentration in the MET-1 reference profilewith β₁ (0.131) results in a predicted concentration of MET-1 in thesample solution of approximately 0.041 wt. %. Likewise, multiplying the0.35 wt. % concentration in the MET-2 reference profile with β₂ (0.752)results in a predicted concentration of MET-2 in the sample solution ofapproximately 0.263 wt. %. Thus, this method for determining theconcentrations of MET-1 and MET-2 can be used to determine “unknown”concentrations of MET-1 and MET-2, even when one is present in a largeexcess (there was over 6 times as much MET-2 in the sample solution ofExample 2, as compared to MET-1), and when the UV-Vis absorbance bandssignificantly overlap (the characteristic peak of MET-1 at 380 nm isdifficult to distinguish due to the overlapping absorbance from MET-2 inthat range).

In Example 3, the same reference absorbance profiles for MET-1 and MET-2as described in Example 1 were used, and these reference profiles areplotted in FIG. 12. A sample solution in which the exact MET-1 and MET-2concentrations were not known was evaluated in Example 3. The only knowninformation on the sample solution was that it contained the samesolvent mixture (1-hexene:toluene at a 9:1 weight ratio) and it had a“target” MET-2 concentration of 0.25 wt. %, although the exactconcentration was not known.

Absorbance spectra for the sample solution of MET-1 and MET-2 in1-hexene:toluene (9:1, weight basis) at a 1 mm path length was obtainedin the same manner as described above, using only 1-hexene/toluene inthe reference cell. The sample absorbance profile for the samplesolution containing both MET-1 and MET-2 is plotted in FIG. 12.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂” wasfit to the sample absorbance profile over the 300-600 nm range. In thisformula, β₁ is the weighting coefficient for MET-1, F₁ is the referenceabsorbance profile for MET-1 (at 0.313 wt. %), β₂ is the weightingcoefficient for MET-2, and F₂ is the reference absorbance profile forMET-2 (at 0.35 wt. %). The model curve for the formula β₁F₁+β₂F₂ isplotted in FIG. 12, where the R² value is 0.99988. In FIG. 12, thesample absorbance profile curve and the model/fitted curve completelyoverlap, and cannot be distinguished visually. For the model curvehaving formula “β₁F₁+β₂F₂” in FIG. 12, β₁ is equal 0.130 for MET-1 andβ₂ is equal to 0.697 for MET-2.

Multiplying the 0.313 wt. % concentration in the MET-1 reference profilewith β₁ (0.130) results in a predicted concentration of MET-1 in thesample solution of approximately 0.041 wt. %. Likewise, multiplying the0.35 wt. % concentration in the MET-2 reference profile with β₂ (0.697)results in a predicted concentration of MET-2 in the sample solution ofapproximately 0.244 wt. %. Thus, this method for determining theconcentrations of MET-1 and MET-2 can be used to determine “unknown”concentrations of MET-1 and MET-2, even when one is present in a largeexcess, and when the UV-Vis absorbance bands significantly overlap.

In Example 4, the same reference absorbance profiles for MET-1 and MET-2as described in Example 1 were used, and these reference profiles areplotted in FIG. 13. A sample solution in which the exact MET-1 and MET-2concentrations were not known was evaluated in Example 4. The only knowninformation on the sample solution was that it contained the samesolvent mixture (1-hexene:toluene at a 9:1 weight ratio) and it had a“target” MET-2 concentration of 0.25 wt. %, although the exactconcentration was not known.

Absorbance spectra for the sample solution of MET-1 and MET-2 in1-hexene:toluene (9:1, weight basis) at a 1 mm path length was obtainedin the same manner as described above, using only 1-hexene/toluene inthe reference cell. The sample absorbance profile for the samplesolution containing both MET-1 and MET-2 is plotted in FIG. 13.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂” wasfit to the sample absorbance profile over the 300-600 nm range. In thisformula, β₁ is the weighting coefficient for MET-1, F₁ is the referenceabsorbance profile for MET-1 (at 0.313 wt. %), β₂ is the weightingcoefficient for MET-2, and F₂ is the reference absorbance profile forMET-2 (at 0.35 wt. %). The model curve for the formula β₁F₁+β₂F₂ isplotted in FIG. 13, where the R² value is 0.99983. In FIG. 13, thesample absorbance profile curve and the model/fitted curve completelyoverlap, and cannot be distinguished visually. For the model curvehaving formula “β₁F₁+β₂F₂” in FIG. 13, β₁ is equal 0.149 for MET-1 andβ₂ is equal to 0.671 for MET-2.

Multiplying the 0.313 wt. % concentration in the MET-1 reference profilewith β₁ (0.149) results in a predicted concentration of MET-1 in thesample solution of approximately 0.047 wt. %. Likewise, multiplying the0.35 wt. % concentration in the MET-2 reference profile with β₂ (0.671)results in a predicted concentration of MET-2 in the sample solution ofapproximately 0.235 wt. %. Thus, this method for determining theconcentrations of MET-1 and MET-2 can be used to determine “unknown”concentrations of MET-1 and MET-2, even when one is present in a largeexcess, and when the UV-Vis absorbance bands significantly overlap.

Solutions Containing Three Transition Metal Compounds

The methods, processes, and reactor systems disclosed herein also can beapplied to a solution containing three or more transition metalcompounds.

In Example 5, a stock solution of MET-1 in 1-hexene:toluene (9:1, weightbasis) was prepared at a concentration of 0.098 wt. %. Absorbancespectra for MET-1 (1 mm path length) at a concentration of 0.098 wt. %was obtained in the same manner as described above, using only solvent(1-hexene/toluene) in the reference cell. This reference absorbanceprofile for MET-1 is plotted in FIG. 14. Similarly, a stock solution ofMET-2 in 1-hexene:toluene (9:1, weight basis) was prepared at aconcentration of 0.202 wt. %. Absorbance spectra for MET-2 (1 mm pathlength) at a concentration of 0.202 wt. % was obtained in the samemanner as described above, using only solvent (1-hexene/toluene) in thereference cell. This reference absorbance profile for MET-2 also isplotted in FIG. 14. Likewise, a stock solution of MET-3 in1-hexene:toluene (9:1, weight basis) was prepared at a concentration of0.190 wt. %. Absorbance spectra for MET-3 (1 mm path length) at aconcentration of 0.190 wt. % was obtained in the same manner asdescribed above, using only solvent (1-hexene/toluene) in the referencecell. This reference absorbance profile for MET-3 also is plotted inFIG. 14.

From the respective stock solutions, a sample solution containing MET-1,MET-2, and MET-3 at known concentrations was prepared: MET-1 (at 0.419wt. %), MET-2 (at 0.247 wt. %), and MET-3 (at 0.161 wt. %). Absorbancespectra for this solution of MET-1, MET-2, and MET-3 in 1-hexene:toluene(9:1, weight basis) at a 1 mm path length was obtained in the samemanner as described above, using only 1-hexene/toluene in the referencecell. This sample absorbance profile for the solution containing MET-1,MET-2, and MET-3 is plotted in FIG. 14.

Using a multiple regression feature in Microsoft Excel, a curve havingthe formula “β₁F₁+β₂F₂+β₃F₃” was fit to the sample absorbance profileover the 350-600 nm range. In this formula, β₁ is the weightingcoefficient for MET-1, F₁ is the reference absorbance profile for MET-1(at 0.098 wt. %), β₂ is the weighting coefficient for MET-2, F₂ is thereference absorbance profile for MET-2 (at 0.202 wt. %), β₃ is theweighting coefficient for MET-3, and F₃ is the reference absorbanceprofile for MET-3 (at 0.190 wt. %). The model curve for the formulaβ₁F₁+β₂F₂+β₃F₃ is plotted in FIG. 14, where the R² value is 0.99887. InFIG. 14, the sample absorbance profile curve and the model/fitted curvealmost completely overlap, and are difficult to be distinguishedvisually. For the model curve having formula “β₁F₁+β₂F₂+β₃F₃” in FIG.14, β₁ is equal to 4.295 for MET-1, β₂ is equal to 1.193 for MET-2, andβ₃ is equal to 0.867 for MET-3. The Sq Res line shows the deviationbetween the model/fitted curve and the sample absorbance profile curve,and by ˜360 nm, it effectively overlaps the baseline, indicating theexcellent fit of the model/fitted curve.

Multiplying the 0.098 wt. % concentration in the MET-1 reference profilewith β₁ (4.295) results in a predicted concentration of MET-1 in thesample solution of approximately 0.421 wt. % (actual is 0.419 wt. %).Likewise, multiplying the 0.202 wt. % concentration in the MET-2reference profile with β₂ (1.193) results in a predicted concentrationof MET-2 in the sample solution of approximately 0.241 wt. % (actual is0.247 wt. %). Similarly, multiplying the 0.190 wt. % concentration inthe MET-3 reference profile with β₃ (0.867) results in a predictedconcentration of MET-3 in the sample solution of approximately 0.165 wt.% (actual is 0.161 wt. %). Thus, this method for simultaneouslydetermining the concentrations of MET-1, MET-2, and MET-3 results invery accurate predictions of the respective concentrations.

In Example 6, the same reference absorbance profiles for MET-1, MET-2,and MET-3 as described in Example 5 were used, and these referenceprofiles are plotted in FIG. 15. A sample solution containing MET-1,MET-2, and MET-3 at known concentrations was prepared: MET-1 (at 0.132wt. %), MET-2 (at 0.184 wt. %), and MET-3 (at 0.265 wt. %). Absorbancespectra for this solution of MET-1, MET-2, and MET-3 in 1-hexene:toluene(9:1, weight basis) at a 1 mm path length was obtained in the samemanner as described above, using only 1-hexene/toluene in the referencecell. This sample absorbance profile for the solution containing MET-1,MET-2, and MET-3 is plotted in FIG. 15.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂+β₃F₃”was fit to the sample absorbance profile over the 350-600 nm range. Inthis formula, β₁ is the weighting coefficient for MET-1, F₁ is thereference absorbance profile for MET-1 (at 0.098 wt. %), β₂ is theweighting coefficient for MET-2, F₂ is the reference absorbance profilefor MET-2 (at 0.202 wt. %), β₃ is the weighting coefficient for MET-3,and F₃ is the reference absorbance profile for MET-3 (at 0.190 wt. %).The model curve for the formula β₁F₁+β₂F₂+β₃F₃ is plotted in FIG. 15,where the R² value is 0.99995. In FIG. 15, the sample absorbance profilecurve and the model/fitted curve completely overlap, and cannot bedistinguished visually. For the model curve having formula“β₁F₁+β₂F₂+β₃F₃” in FIG. 15, β₁ is equal to 1.190 for MET-1, β₂ is equalto 0.924 for MET-2, and β₃ is equal to 1.539 for MET-3. The Sq Res lineshows the deviation between the model/fitted curve and the sampleabsorbance profile curve, and by ˜360 nm, it effectively overlaps thebaseline, indicating the excellent fit of the model/fitted curve.

Multiplying the 0.098 wt. % concentration in the MET-1 reference profilewith β₁ (1.190) results in a predicted concentration of MET-1 in thesample solution of approximately 0.117 wt. % (actual is 0.132 wt. %).Likewise, multiplying the 0.202 wt. % concentration in the MET-2reference profile with β₂ (0.924) results in a predicted concentrationof MET-2 in the sample solution of approximately 0.187 wt. % (actual is0.184 wt. %). Similarly, multiplying the 0.190 wt. % concentration inthe MET-3 reference profile with β₃ (1.539) results in a predictedconcentration of MET-3 in the sample solution of approximately 0.292 wt.% (actual is 0.265 wt. %). Thus, this method for simultaneouslydetermining the concentrations of MET-1, MET-2, and MET-3 results invery accurate predictions of the respective concentrations.

In Example 7, the same reference absorbance profiles for MET-1, MET-2,and MET-3 as described in Example 5 were used, and these referenceprofiles are plotted in FIG. 16. A sample solution containing MET-1,MET-2, and MET-3 at known concentrations was prepared: MET-1 (at 0.196wt. %), MET-2 (at 0.121 wt. %), and MET-3 (at 0.184 wt. %). Absorbancespectra for this solution of MET-1, MET-2, and MET-3 in 1-hexene:toluene(9:1, weight basis) at a 1 mm path length was obtained in the samemanner as described above, using only 1-hexene/toluene in the referencecell. This sample absorbance profile for the solution containing MET-1,MET-2, and MET-3 is plotted in FIG. 16.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂+β₃F₃”was fit to the sample absorbance profile over the 300-600 nm range. Inthis formula, β₁ is the weighting coefficient for MET-1, F₁ is thereference absorbance profile for MET-1 (at 0.098 wt. %), β₂ is theweighting coefficient for MET-2, F₂ is the reference absorbance profilefor MET-2 (at 0.202 wt. %), β₃ is the weighting coefficient for MET-3,and F₃ is the reference absorbance profile for MET-3 (at 0.190 wt. %).The model curve for the formula β₁F₁+β₂F₂+β₃F₃ is plotted in FIG. 16,where the R² value is 0.99998. In FIG. 16, the sample absorbance profilecurve and the model/fitted curve completely overlap, and cannot bedistinguished visually. For the model curve having formula“β₁F₁+β₂F₂+β₃F₃” in FIG. 16, β₁ is equal to 1.959 for MET-1, β₂ is equalto 0.578 for MET-2, and β₃ is equal to 0.988 for MET-3. The Sq Res lineshows the deviation between the model/fitted curve and the sampleabsorbance profile curve, and by 350 nm, it effectively overlaps thebaseline, indicating the excellent fit of the model/fitted curve.

Multiplying the 0.098 wt. % concentration in the MET-1 reference profilewith β₁ (1.959) results in a predicted concentration of MET-1 in thesample solution of approximately 0.192 wt. % (actual is 0.196 wt. %).Likewise, multiplying the 0.202 wt. % concentration in the MET-2reference profile with β₂ (0.578) results in a predicted concentrationof MET-2 in the sample solution of approximately 0.117 wt. % (actual is0.121 wt. %). Similarly, multiplying the 0.190 wt. % concentration inthe MET-3 reference profile with β₃ (0.988) results in a predictedconcentration of MET-3 in the sample solution of approximately 0.188 wt.% (actual is 0.184 wt. %). Thus, this method for simultaneouslydetermining the concentrations of MET-1, MET-2, and MET-3 results invery accurate predictions of the respective concentrations.

In Example 8, the same reference absorbance profiles for MET-1, MET-2,and MET-3 as described in Example 5 were used, and these referenceprofiles are plotted in FIG. 17. A sample solution containing MET-1,MET-2, and MET-3 at known concentrations was prepared: MET-1 (at 0.033wt. %), MET-2 (at 0.067 wt. %), and MET-3 (at 0.063 wt. %). Absorbancespectra for this solution of MET-1, MET-2, and MET-3 in 1-hexene:toluene(9:1, weight basis) at a 1 mm path length was obtained in the samemanner as described above, using only 1-hexene/toluene in the referencecell. This sample absorbance profile for the solution containing MET-1,MET-2, and MET-3 is plotted in FIG. 17.

Using multiple regression, a curve having the formula “β₁F₁+β₂F₂+β₃F₃”was fit to the sample absorbance profile over the 300-600 nm range. Inthis formula, β₁ is the weighting coefficient for MET-1, F₁ is thereference absorbance profile for MET-1 (at 0.098 wt. %), β₂ is theweighting coefficient for MET-2, F₂ is the reference absorbance profilefor MET-2 (at 0.202 wt. %), β₃ is the weighting coefficient for MET-3,and F₃ is the reference absorbance profile for MET-3 (at 0.190 wt. %).The model curve for the formula β₁F₁+β₂F₂+β₃F₃ is plotted in FIG. 17,where the R² value is 0.99975. In FIG. 17, the sample absorbance profilecurve and the model/fitted curve completely overlap, and cannot bedistinguished visually. For the model curve having formula“β₁F₁+β₂F₂+β₃F₃” in FIG. 17, β₁ is equal to 0.341 for MET-1, β₂ is equalto 0.330 for MET-2, and β₃ is equal to 0.350 for MET-3. The Sq Res lineshows the deviation between the model/fitted curve and the sampleabsorbance profile curve, and by ˜310 nm, it effectively overlaps thebaseline, indicating the excellent fit of the model/fitted curve.

Multiplying the 0.098 wt. % concentration in the MET-1 reference profilewith β₁ (0.341) results in a predicted concentration of MET-1 in thesample solution of approximately 0.033 wt. % (actual is 0.033 wt. %).Likewise, multiplying the 0.202 wt. % concentration in the MET-2reference profile with β₂ (0.330) results in a predicted concentrationof MET-2 in the sample solution of approximately 0.067 wt. % (actual is0.067 wt. %). Similarly, multiplying the 0.190 wt. % concentration inthe MET-3 reference profile with β₃ (0.350) results in a predictedconcentration of MET-3 in the sample solution of approximately 0.067 wt.% (actual is 0.063 wt. %). Thus, this method for simultaneouslydetermining the concentrations of MET-1, MET-2, and MET-3 results invery accurate predictions of the respective concentrations.

The invention is described above with reference to numerous aspects andspecific examples. Many variations will suggest themselves to thoseskilled in the art in light of the above detailed description. All suchobvious variations are within the full intended scope of the appendedclaims. Other aspects of the invention can include, but are not limitedto, the following (aspects are described as “comprising” but,alternatively, can “consist essentially of” or “consist of” unlessspecifically stated otherwise):

Aspect 1. A method for determining a first concentration of a firsttransition metal compound and a second concentration of a secondtransition metal compound in a solution comprising the first transitionmetal compound and the second transition metal compound, the methodcomprising:

(i) providing a first reference absorbance profile (F₁) of the firsttransition metal compound in a first reference solution at a first knownconcentration, and a second reference absorbance profile (F₂) of thesecond transition metal compound in a second reference solution at asecond known concentration;

(ii) submitting a sample of the solution to a sample chamber;

(iii) irradiating the sample in the chamber with a light beam at awavelength in the UV-visible spectrum;

(iv) generating a sample absorbance profile of the sample, andcalculating a curve having the formula β₁F₁+β₂F₂ to fit the sampleabsorbance profile to a least-squares regression fit value (R²) of atleast 0.9; wherein:

β₁ is a first weighting coefficient;

F₁ is the first reference absorbance profile of the first transitionmetal compound in the first reference solution at the first knownconcentration;

β₂ is a second weighting coefficient; and

F₂ is the second reference absorbance profile of the second transitionmetal compound in the second reference solution at the second knownconcentration; and

(v) multiplying the first known concentration with β₁ to determine thefirst concentration of the first transition metal compound in thesolution, and multiplying the second known concentration with β₂ todetermine the second concentration of the second transition metalcompound in the solution.

Aspect 2. The method defined in aspect 1, wherein the solutioncomprising the first transition metal compound and the second transitionmetal compound is a feed stream to a catalyst preparation vessel.

Aspect 3. The method defined in aspect 1, wherein the solutioncomprising the first transition metal compound and the second transitionmetal compound is a liquid (or homogeneous) catalyst system comprisingthe first transition metal compound, the second transition metalcompound, and other catalyst components.

Aspect 4. The method defined in aspect 1, wherein the solutioncomprising the first transition metal compound and the second transitionmetal compound is a solution of a heterogeneous catalyst system (e.g., asolution prepared from a sample mixture of the catalyst system, such asfrom a catalyst preparation vessel), or a solution from a polymerizationreactor (e.g., a solution prepared from a sample mixture from apolymerization reactor). Aspect 5. A process for operating apolymerization reactor system, the process comprising:

(I) contacting a catalyst system comprising a first transition metalcompound, a second transition metal compound, an activator, and anoptional co-catalyst, with an olefin monomer and an optional olefincomonomer in a reactor within the polymerization reactor system underpolymerization reaction conditions to produce an olefin polymer;

(II) determining a first concentration of the first transition metalcompound and a second concentration of the second transition metalcompound in a solution comprising the first transition metal compoundand the second transition metal compound, the first concentration andthe second concentration determined by the method defined in aspect 1;and

(III) adjusting a first flow rate of the first transition metal compoundand/or a second flow rate of second transition metal compound into thereactor when the first concentration and/or the second concentration hasreached a predetermined level (or adjusting the first flow rate of thefirst transition metal compound based on the first determinedconcentration and/or adjusting the second flow rate of the secondtransition metal compound based on the second determined concentration).

Aspect 6. The process defined in aspect 5, wherein the solutioncomprising the first transition metal compound and the second transitionmetal compound is a feed stream to a catalyst preparation vessel, andthe first flow rate and/or the second flow rate is/are controlled byadjusting a flow rate of a feed stream to the catalyst preparationvessel, and/or by adjusting a relative flow rate (ratio of first:secondtransition metal compound) to the catalyst preparation vessel, and/or byadjusting a flow rate of the catalyst system exiting the catalystpreparation vessel and entering the reactor.

Aspect 7. The process defined in aspect 5, wherein the catalyst systemis a liquid (or homogeneous) catalyst system, and the solutioncomprising the first transition metal compound and the second transitionmetal compound is a sample of the liquid catalyst system, and whereinthe first flow rate and/or the second flow rate is/are controlled byadjusting a relative flow rate (ratio of first:second transition metalcompound) to the reactor, and/or by adjusting a flow rate of the liquidcatalyst system entering the reactor.

Aspect 8. The process defined in aspect 5, wherein the polymerizationreactor system comprises a polymerization reactor containing a mixture,and the solution comprising the first transition metal compound and thesecond transition metal compound is a solution prepared from a sample ofthe mixture from the polymerization reactor (e.g., a solutionpolymerization reactor, a slurry polymerization reactor), and whereinthe first flow rate and/or the second flow rate is/are controlled byadjusting a relative flow rate (ratio of first:second transition metalcompound) to the reactor, and/or by adjusting a flow rate of thecatalyst system entering the polymerization reactor.

Aspect 9. The method or process defined in any one of the precedingaspects, wherein the sample chamber comprises a flow cell.

Aspect 10. The method or process defined in any one of aspects 1-9,wherein the wavelength is a single wavelength.

Aspect 11. The method or process defined in any one of aspects 1-9,wherein the wavelength is a range of wavelengths (e.g., a 200 nm or a300 nm wavelength range).

Aspect 12. The method or process defined in any one of aspects 1-9 or11, wherein the wavelength comprises wavelengths in the visible spectrum(from 380 nm to 780 nm).

Aspect 13. The method or process defined in any one of aspects 1-9 or11, wherein the wavelength comprises wavelengths in the 200 nm to 750 nmrange.

Aspect 14. The method or process defined in any one of aspects 1-9 or11, wherein the wavelength comprises wavelengths in the 300 nm to 600 nmrange.

Aspect 15. The method or process defined in any one of aspects 1-14,wherein the sample (or first reference, or second reference) absorbanceprofile comprises an absorbance peak at a single wavelength.

Aspect 16. The method or process defined in any one of aspects 1-14,wherein the sample (or first reference, or second reference) absorbanceprofile comprises an absorbance curve (e.g., peaks and/or areas undercurves) over a range of wavelengths from 200 nm to 750 nm, or from 300nm to 600 nm.

Aspect 17. The method or process defined in any one of aspects 1-14 or16, wherein the sample (or first reference, or second reference)absorbance profile comprises an absorbance curve over a subset ofwavelengths spanning less than 350 nm, less than 300 nm, less than 250nm, less than 200 nm, or less than 150 nm.

Aspect 18. The method or process defined in any one of aspects 1-17,wherein the curve having the formula β₁F₁+β₂F₂ is determined over arange of wavelengths, e.g., from 200 nm to 750 nm, from 300 nm to 600nm, from 350 nm to 600 nm, or from 350 nm to 550 nm, to fit the sampleabsorbance profile.

Aspect 19. The method or process defined in any one of aspects 1-18,wherein the curve having the formula β₁F₁+β₂F₂ is determined over asubset of wavelengths, e.g., spanning less than 350 nm, less than 300nm, less than 250 nm, less than 200 nm, or less than 100 nm, in the 200nm to 750 nm, or the 300 nm to 600 nm wavelength range, to fit thesample absorbance profile.

Aspect 20. The method or process defined in any one of the precedingaspects, wherein the least-squares regression fit value (R²) is at least0.98, at least 0.99, at least 0.999, or at least 0.9995.

Aspect 21. The method or process defined in any one of aspects 1-20,wherein the solution (comprising the first transition metal compound andthe second transition metal compound), the first reference solution, andthe second reference solution comprise the same solvent (e.g., the samehydrocarbon solvent).

Aspect 22. The method or process defined in any one of aspects 1-20,wherein at least two of the solution (comprising the first transitionmetal compound and the second transition metal compound), the firstreference solution, and the second reference solution comprise adifferent solvent (e.g., a different hydrocarbon solvent).

Aspect 23. A polymerization reactor system comprising:

(A) a reactor configured to contact a catalyst system with an olefinmonomer and an optional olefin comonomer under polymerization reactionconditions to produce an olefin polymer;

(B) a catalyst preparation vessel configured to contact a firsttransition metal compound, a second transition metal compound, anactivator, and an optional co-catalyst to form the catalyst system; and

(C) an analytical system configured to determine a first concentrationof the first transition metal compound and a second concentration of thesecond transition metal compound in a solution comprising the firsttransition metal compound and the second transition metal compoundpresent within the polymerization reactor system.

Aspect 24. The system defined in aspect 23, wherein the analyticalsystem comprises an ultraviolet-visible spectrometer with an integratedcomputer system

(a) for measuring a sample absorbance profile of the solution;

(b) for calculating a curve having the formula β₁F₁+β₂F₂ to fit thesample absorbance profile to a least-squares regression fit value (R²)of at least 0.9, wherein:

β₁ is a first weighting coefficient;

F₁ is a first reference absorbance profile of the first transition metalcompound in a first reference solution at a first known concentration;

β₂ is a second weighting coefficient; and

F₂ is a second reference absorbance profile of the second transitionmetal compound in a second reference solution at a second knownconcentration; and

(c) for multiplying the first known concentration with β₁ to determinethe first concentration of the first transition metal compound in thesolution, and multiplying the second known concentration with β₂ todetermine the second concentration of the second transition metalcompound in the solution.

Aspect 25. The system defined in aspect 23, wherein the analyticalsystem comprises an ultraviolet-visible spectrometer and an externalcomputer system, the ultraviolet-visible spectrometer configured to (a)measure a sample absorbance profile of the solution, and the externalcomputer system configured to

(b) calculate a curve having the formula β₁F₁+β₂F₂ to fit the sampleabsorbance profile to a least-squares regression fit value (R²) of atleast 0.9, wherein:

β₁ is a first weighting coefficient;

F₁ is a first reference absorbance profile of the first transition metalcompound in a first reference solution at a first known concentration;

β₂ is a second weighting coefficient; and

F₂ is a second reference absorbance profile of the second transitionmetal compound in a second reference solution at a second knownconcentration; and

(c) multiply the first known concentration with β₁ to determine thefirst concentration of the first transition metal compound in thesolution, and multiplying the second known concentration with β₂ todetermine the second concentration of the second transition metalcompound in the solution.

Aspect 26. The system defined in any one of aspects 24-25, wherein theanalytical system further comprises a filter assembly configured tofilter a sample of the solution before analysis by theultraviolet-visible spectrometer.

Aspect 27. The system defined in any one of aspects 24-26, wherein thesample (or first reference, or second reference) absorbance profilecomprises an absorbance peak at a single wavelength.

Aspect 28. The system defined in any one of aspects 24-26, wherein thesample (or first reference, or second reference) absorbance profilecomprises an absorbance curve (e.g., peaks and/or areas under curves)over a range of wavelengths from 200 nm to 750 nm, or from 300 nm to 600nm.

Aspect 29. The system defined in any one of aspects 24-26 or 28, whereinthe sample (or first reference, or second reference) absorbance profilecomprises an absorbance curve over a subset of wavelengths spanning lessthan 350 nm, less than 300 nm, less than 250 nm, less than 200 nm, orless than 150 nm.

Aspect 30. The system defined in any one of aspects 24-29, wherein thesolution (comprising the first transition metal compound and the secondtransition metal compound), the first reference solution, and the secondreference solution comprise the same solvent (e.g., the same hydrocarbonsolvent).

Aspect 31. The system defined in any one of aspects 24-29, wherein atleast two of the solution (comprising the first transition metalcompound and the second transition metal compound), the first referencesolution, and the second reference solution comprise a different solvent(e.g., a different hydrocarbon solvent).

Aspect 32. The system defined in any one of aspects 23-31, wherein thereactor system further comprises (D) a controller configured to controla first flow rate of the first transition metal compound and/or a secondflow rate of second transition metal compound into the reactor based on(or according to) the first concentration and/or the secondconcentration determined by the analytical system.

Aspect 33. The system defined in aspect 32, wherein the controllercomprises a processing unit.

Aspect 34. The system defined in any one of aspects 32-33, wherein thesolution comprising the first transition metal compound and the secondtransition metal compound is a feed stream to a catalyst preparationvessel, and the controller controls the first flow rate and/or thesecond flow rate into the reactor by adjusting a flow rate of the feedstream to the catalyst preparation vessel, and/or by adjusting arelative flow rate (ratio of first:second transition metal compound) tothe catalyst preparation vessel, and/or by adjusting a flow rate of thecatalyst system exiting the catalyst preparation vessel and entering thereactor.

Aspect 35. The system defined in any one of aspects 32-33, wherein thecatalyst system is a liquid (or homogeneous) catalyst system, and thesolution comprising the first transition metal compound and the secondtransition metal compound is a sample of the liquid catalyst system, andwherein the controller controls the first flow rate and/or the secondflow rate into the reactor by adjusting a relative flow rate (ratio offirst:second transition metal compound) to the reactor, and/or byadjusting a flow rate of the liquid catalyst system entering thereactor.

Aspect 36. The system defined in any one of aspects 32-33, wherein thepolymerization reactor system comprises a polymerization reactorcontaining a mixture, and the solution comprising the first transitionmetal compound and the second transition metal compound is a solutionprepared from a sample of the mixture from the polymerization reactor(e.g., a solution polymerization reactor, a slurry polymerizationreactor), and wherein the controller controls the first flow rate and/orthe second flow rate by adjusting a relative flow rate (ratio offirst:second transition metal compound) to the reactor, and/or byadjusting a flow rate of the catalyst system entering the polymerizationreactor.

Aspect 37. The process or system defined in any one of aspects 5-36,wherein the reactor system comprises one reactor.

Aspect 38. The process or system defined in any one of aspects 5-36,wherein the reactor system comprises two or more reactors.

Aspect 39. The process or system defined in any one of aspects 5-38,wherein the reactor system comprises a solution reactor, gas-phasereactor, slurry reactor, or a combination thereof.

Aspect 40. The process or system defined in any one of aspects 5-39,wherein the reactor system comprises a loop slurry reactor.

Aspect 41. The process or system defined in any one of aspects 5-40,wherein the polymerization reaction conditions comprise a polymerizationreaction temperature in a range from about 60° C. to about 185° C., fromabout 60° C. to about 115° C., or from about 130° C. to about 180° C.,and any suitable reaction pressure, e.g., from about 200 to about 1000psig.

Aspect 42. The process or system defined in any one of aspects 5-41,wherein the catalyst system comprises a solid oxide.

Aspect 43. The process or system defined in any one of aspects 5-41,wherein the activator comprises an activator-support (e.g., fluoridedsilica-coated alumina or sulfated alumina).

Aspect 44. The process or system defined in any one of aspects 5-41,wherein the activator comprises an aluminoxane.

Aspect 45. The process or system defined in any one of aspects 5-44,wherein the catalyst system comprises a co-catalyst.

Aspect 46. The process or system defined in any one of aspects 5-44,wherein the catalyst system comprises an organoaluminum co-catalyst.

Aspect 47. The process or system defined in any one of aspects 5-46,wherein the olefin monomer comprises a C₂-C₂₄ olefin.

Aspect 48. The process or system defined in any one of aspects 5-47,wherein the olefin monomer comprises propylene.

Aspect 49. The process or system defined in any one of aspects 5-47,wherein the olefin monomer comprises ethylene.

Aspect 50. The process or system defined in any one of aspects 5-47,wherein the catalyst system is contacted with ethylene and an olefincomonomer comprising 1-butene, 1-hexene, 1-octene, or a mixture thereof.

Aspect 51. The process or system defined in any one of aspects 5-47,wherein the olefin polymer comprises an ethylene homopolymer, anethylene copolymer, a propylene homopolymer, or a propylene-basedcopolymer.

Aspect 52. The process or system defined in any one of aspects 5-47,wherein the olefin polymer comprises an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, or an ethylene/1-octene copolymer.

Aspect 53. The method, process, or system defined in any one of aspects1-52, wherein the first transition metal compound and the secondtransition metal compound, independently, comprise any suitablenon-metallocene compound.

Aspect 54. The method, process, or system defined in any one of aspects1-52, wherein the first transition metal compound and the secondtransition metal compound, independently, comprise any suitablemetallocene compound.

Aspect 55. The method, process, or system defined in any one of aspects1-52, wherein the first transition metal compound and the secondtransition metal compound, independently, comprise chromium, vanadium,titanium, zirconium, hafnium, or a combination thereof.

Aspect 56. The method, process, or system defined in any one of aspects1-52, wherein at least one of the first transition metal compound andthe second transition metal compound is a bridged metallocene compound.

Aspect 57. The method, process, or system defined in any one of aspects1-52, wherein at least one of the first transition metal compound andthe second transition metal compound is an unbridged metallocenecompound.

Aspect 58. The method, process, or system defined in any one of aspects1-57, wherein the solution comprises the first transition metalcompound, the second transition metal compound, and a hydrocarbonsolvent.

Aspect 59. The method, process, or system defined in any one of aspects1-57, wherein the solution comprises the first transition metalcompound, the second transition metal compound, and a hydrocarbonsolvent comprising 1-hexene, isobutane, toluene, or cyclohexene, as wellas mixtures or combinations thereof.

Aspect 60. The method, process, or system defined in any one of aspects1-59, wherein a weight ratio of the first transition metal compound tothe second transition metal compound in the solution is in a range fromabout 50:1 to about 1:50, from about 10:1 to about 1:10, from about 2:1to about 1:2, from about 1:20 to about 1:1, etc.

Aspect 61. A method for determining a first concentration of a firsttransition metal compound, a second concentration of a second transitionmetal compound, and a third concentration of a third transition metalcompound in a solution comprising the first transition metal compound,the second transition metal compound, and the third transition metalcompound, the method comprising:

(i) providing a first reference absorbance profile (F₁) of the firsttransition metal compound in a first reference solution at a first knownconcentration, a second reference absorbance profile (F₂) of the secondtransition metal compound in a second reference solution at a secondknown concentration, and a third reference absorbance profile (F₃) ofthe third transition metal compound in a third reference solution at athird known concentration;

(ii) submitting a sample of the solution to a sample chamber;

(iii) irradiating the sample in the chamber with a light beam at awavelength in the UV-visible spectrum;

(iv) generating a sample absorbance profile of the sample, andcalculating a curve having the formula β₁F₁+β₂F₂+β₃F₃ to fit the sampleabsorbance profile to a least-squares regression fit value (R²) of atleast 0.9; wherein:

β₁ is a first weighting coefficient;

F₁ is the first reference absorbance profile of the first transitionmetal compound in the first reference solution at the first knownconcentration;

β₂ is a second weighting coefficient;

F₂ is the second reference absorbance profile of the second transitionmetal compound in the second reference solution at the second knownconcentration;

β₃ is a third weighting coefficient; and

F₃ is the third reference absorbance profile of the third transitionmetal compound in the third reference solution at the third knownconcentration; and

(v) multiplying the first known concentration with β₁ to determine thefirst concentration of the first transition metal compound in thesolution, multiplying the second known concentration with β₂ todetermine the second concentration of the second transition metalcompound in the solution, and multiplying the third known concentrationwith β₃ to determine the third concentration of the third transitionmetal compound in the solution.

Aspect 62. A process for operating a polymerization reactor system, theprocess comprising:

(I) contacting a catalyst system comprising a first transition metalcompound, a second transition metal compound, a third transition metalcompound, an activator, and an optional co-catalyst, with an olefinmonomer and an optional olefin comonomer in a reactor within thepolymerization reactor system under polymerization reaction conditionsto produce an olefin polymer;

(II) determining a first concentration of the first transition metalcompound, a second concentration of the second transition metalcompound, and a third concentration of the third transition metalcompound in a solution comprising the first transition metal compound,the second transition metal compound, and the third transition metalcompound, the first concentration, the second concentration, and thethird concentration determined by the method defined in aspect 61; and

(III) adjusting a first flow rate of the first transition metalcompound, a second flow rate of second transition metal compound, and/ora third flow rate of the third transition metal compound into thereactor when the first concentration, the second concentration, and/orthe third concentration has reached a predetermined level (or adjustingthe first flow rate of the first transition metal compound based on thefirst determined concentration, adjusting the second flow rate of thesecond transition metal compound based on the second determinedconcentration, and/or adjusting the third flow rate of the thirdtransition metal compound based on the third determined concentration).

We claim:
 1. A polymerization reactor system comprising: (A) a reactorconfigured to contact a catalyst system with an olefin monomer and anoptional olefin comonomer under polymerization reaction conditions toproduce an olefin polymer; (B) a catalyst preparation vessel configuredto contact a first transition metal compound, a second transition metalcompound, an activator, and an optional co-catalyst to form the catalystsystem; and (C) an analytical system configured to determine a firstconcentration of the first transition metal compound and a secondconcentration of the second transition metal compound in a solutioncomprising the first transition metal compound and the second transitionmetal compound present within the polymerization reactor system;wherein: the polymerization reactor system comprises a slurry reactor, agas-phase reactor, a solution reactor, or a combination thereof.
 2. Thereactor system of claim 1, wherein the analytical system comprises anultraviolet-visible spectrometer.
 3. The reactor system of claim 2,wherein the analytical system further comprises a filter assemblyconfigured to filter a sample of the solution comprising the firsttransition metal compound and the second transition metal compoundbefore analysis by the ultraviolet-visible spectrometer.
 4. The reactorsystem of claim 1, wherein the reactor system further comprises (D) acontroller configured to control a first flow rate of the firsttransition metal compound and/or a second flow rate of the secondtransition metal compound into the reactor based on the firstconcentration and/or the second concentration determined by theanalytical system.
 5. The reactor system of claim 4, wherein: theanalytical system comprises an ultraviolet-visible spectrometer with anintegrated computer system: (a) for measuring a sample absorbanceprofile of the solution; (b) for calculating a curve having the formulaβ₁F₁+β₂F₂ to fit the sample absorbance profile to a least-squaresregression fit value (R²) of at least 0.9, wherein: β₁ is a firstweighting coefficient; F₁ is a first reference absorbance profile of thefirst transition metal compound in a first reference solution at a firstknown concentration; β₂ is a second weighting coefficient; and F₂ is asecond reference absorbance profile of the second transition metalcompound in a second reference solution at a second known concentration;and (c) for multiplying the first known concentration with β₁ todetermine the first concentration of the first transition metal compoundin the solution, and multiplying the second known concentration with β₂to determine the second concentration of the second transition metalcompound in the solution.
 6. The reactor system of claim 4, wherein: thesolution comprises the first transition metal compound, the secondtransition metal compound, and a hydrocarbon solvent; and the solutionis a feed stream to the catalyst preparation vessel, and the controllercontrols the first flow rate and/or the second flow rate into thereactor by adjusting a flow rate ratio of the first:second transitionmetal compound to the catalyst preparation vessel, and/or by adjusting aflow rate of the catalyst system exiting the catalyst preparation vesseland entering the reactor.
 7. The reactor system of claim 4, wherein thecontroller is configured to control the first flow rate and/or thesecond flow rate based on the first concentration and/or the secondconcentration determined by the analytical system in real-time.
 8. Thereactor system of claim 4, wherein: the reactor system comprises two ormore reactors, at least one of which is a loop slurry reactor; thepolymerization reaction conditions comprise a reaction temperature in arange from about 60° C. to about 185° C., and a reaction pressure ofless than about 1000 psig; the olefin polymer comprises an ethylenehomopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexenecopolymer, or an ethylene/1-octene copolymer; and the first transitionmetal compound and the second transition metal compound independentlycomprise a bridged or unbridged metallocene compound.
 9. Apolymerization reactor system comprising: (A) a loop slurry reactorconfigured to contact a catalyst system with ethylene and an optionalolefin comonomer under polymerization reaction conditions to produce anethylene polymer; (B) a catalyst preparation vessel configured tocontact a first transition metal compound, a second transition metalcompound, an activator, and an optional co-catalyst to form the catalystsystem; and (C) an analytical system configured to determine a firstconcentration of the first transition metal compound and a secondconcentration of the second transition metal compound in a solutioncomprising the first transition metal compound and the second transitionmetal compound present within the polymerization reactor system.
 10. Thereactor system of claim 9, wherein the reactor system further comprises(D) a controller configured to control a first flow rate of the firsttransition metal compound and/or a second flow rate of the secondtransition metal compound into the loop slurry reactor based on thefirst concentration and/or the second concentration determined by theanalytical system.
 11. The reactor system of claim 9, wherein theanalytical system comprises an ultraviolet-visible spectrometer.
 12. Thereactor system of claim 11, wherein the analytical system furthercomprises a filter assembly configured to filter a sample of thesolution comprising the first transition metal compound and the secondtransition metal compound before analysis by the ultraviolet-visiblespectrometer.
 13. The reactor system of claim 9, wherein the analyticalsystem comprises an ultraviolet-visible spectrometer with an integratedcomputer system (a) for measuring a sample absorbance profile of thesolution; (b) for calculating a curve having the formula β₁F₁+β₂F₂ tofit the sample absorbance profile to a least-squares regression fitvalue (R²) of at least 0.9, wherein: β₁ is a first weightingcoefficient; F₁ is a first reference absorbance profile of the firsttransition metal compound in a first reference solution at a first knownconcentration; β₂ is a second weighting coefficient; and F₂ is a secondreference absorbance profile of the second transition metal compound ina second reference solution at a second known concentration; and (c) formultiplying the first known concentration with β₁ to determine the firstconcentration of the first transition metal compound in the solution,and multiplying the second known concentration with β₂ to determine thesecond concentration of the second transition metal compound in thesolution.
 14. The reactor system of claim 9, wherein the analyticalsystem comprises an ultraviolet-visible spectrometer and an externalcomputer system, the ultraviolet-visible spectrometer configured to (a)measure a sample absorbance profile of the solution, and the externalcomputer system configured to (b) calculate a curve having the formulaβ₁F₁+β₂F₂ to fit the sample absorbance profile to a least-squaresregression fit value (R²) of at least 0.9, wherein: β₁ is a firstweighting coefficient; F₁ is a first reference absorbance profile of thefirst transition metal compound in a first reference solution at a firstknown concentration; β₂ is a second weighting coefficient; and F₂ is asecond reference absorbance profile of the second transition metalcompound in a second reference solution at a second known concentration;and (c) multiply the first known concentration with β₁ to determine thefirst concentration of the first transition metal compound in thesolution, and multiplying the second known concentration with β₂ todetermine the second concentration of the second transition metalcompound in the solution.
 15. The reactor system of claim 9, wherein:the analytical system comprises an ultraviolet-visible spectrometer; andthe reactor system further comprises (D) a controller configured tocontrol a first flow rate of the first transition metal compound and/ora second flow rate of the second transition metal compound into the loopslurry reactor based on the first concentration and/or the secondconcentration determined by the analytical system.
 16. The reactorsystem of claim 15, wherein the solution comprises the first transitionmetal compound, the second transition metal compound, and a hydrocarbonsolvent.
 17. The reactor system of claim 15, wherein: the ethylenepolymer comprises an ethylene homopolymer, an ethylene/1-butenecopolymer, an ethylene/1-hexene copolymer, or an ethylene/1-octenecopolymer; and the first transition metal compound and the secondtransition metal compound independently comprise a bridged or unbridgedmetallocene compound.
 18. The reactor system of claim 15, wherein thepolymerization reaction conditions comprise a reaction temperature in arange from about 60° C. to about 185° C., and a reaction pressure ofless than about 1000 psig.
 19. The reactor system of claim 15, wherein:the solution is a feed stream to the catalyst preparation vessel; andthe controller controls the first flow rate and/or the second flow rateinto the loop slurry reactor by adjusting a flow rate ratio of thefirst:second transition metal compound to the catalyst preparationvessel, and/or by adjusting a flow rate of the catalyst system exitingthe catalyst preparation vessel and entering the loop slurry reactor.20. The reactor system of claim 15, wherein: the loop slurry reactorcontains a mixture; the solution comprising the first transition metalcompound and the second transition metal compound is a solution preparedfrom a sample of the mixture from the loop slurry reactor; and thecontroller controls the first flow rate and/or the second flow rate byadjusting a relative flow rate of the first and second transition metalcompounds to the loop slurry reactor, and/or by adjusting a flow rate ofthe catalyst system entering the loop slurry reactor.